I’ve found the logs ! There are in /var/log/onlyoffice/documentserver/nginx.error.log.
~# cat /var/log/onlyoffice/documentserver/nginx.error.log
2020/11/25 18:07:47 [error] 32293#32293: *190 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/ HTTP/1.1", upstream: "http://127.0.0.1:3000/", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/welcome/"
2020/11/25 18:07:47 [error] 32293#32293: *190 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/ HTTP/1.1", upstream: "http://[::1]:3000/", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/welcome/"
2020/11/25 18:07:59 [error] 32293#32293: *196 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/ HTTP/1.1", upstream: "http://[::1]:3000/", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/welcome/"
2020/11/25 18:07:59 [error] 32293#32293: *196 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/ HTTP/1.1", upstream: "http://127.0.0.1:3000/", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/welcome/"
2020/11/25 18:08:19 [error] 32291#32291: *204 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/ HTTP/1.1", upstream: "http://127.0.0.1:3000/", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/welcome/"
2020/11/25 18:08:19 [error] 32291#32291: *204 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/ HTTP/1.1", upstream: "http://[::1]:3000/", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/welcome/"
2020/11/25 18:08:22 [error] 32291#32291: *211 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/stylesheet.css HTTP/1.1", upstream: "http://example/stylesheets/stylesheet.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *213 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/jquery-ui.css HTTP/1.1", upstream: "http://example/stylesheets/jquery-ui.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *215 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/images/logo.png HTTP/1.1", upstream: "http://example/images/logo.png", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *217 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery-1.8.2.js HTTP/1.1", upstream: "http://example/javascripts/jquery-1.8.2.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *219 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery-ui.js HTTP/1.1", upstream: "http://example/javascripts/jquery-ui.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *221 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.blockUI.js HTTP/1.1", upstream: "http://example/javascripts/jquery.blockUI.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *223 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.iframe-transport.js HTTP/1.1", upstream: "http://example/javascripts/jquery.iframe-transport.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *225 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.fileupload.js HTTP/1.1", upstream: "http://example/javascripts/jquery.fileupload.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *227 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.dropdownToggle.js HTTP/1.1", upstream: "http://example/javascripts/jquery.dropdownToggle.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *232 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/stylesheet.css HTTP/1.1", upstream: "http://example/stylesheets/stylesheet.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *234 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/jquery-ui.css HTTP/1.1", upstream: "http://example/stylesheets/jquery-ui.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *236 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/images/logo.png HTTP/1.1", upstream: "http://example/images/logo.png", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *238 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery-1.8.2.js HTTP/1.1", upstream: "http://example/javascripts/jquery-1.8.2.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *240 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery-ui.js HTTP/1.1", upstream: "http://example/javascripts/jquery-ui.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *242 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.blockUI.js HTTP/1.1", upstream: "http://example/javascripts/jquery.blockUI.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *244 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.iframe-transport.js HTTP/1.1", upstream: "http://example/javascripts/jquery.iframe-transport.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *246 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.fileupload.js HTTP/1.1", upstream: "http://example/javascripts/jquery.fileupload.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *248 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.dropdownToggle.js HTTP/1.1", upstream: "http://example/javascripts/jquery.dropdownToggle.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:22 [error] 32291#32291: *250 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/images/favicon.ico HTTP/1.1", upstream: "http://example/images/favicon.ico", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *257 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/stylesheet.css HTTP/1.1", upstream: "http://example/stylesheets/stylesheet.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *259 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/jquery-ui.css HTTP/1.1", upstream: "http://example/stylesheets/jquery-ui.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *261 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/images/logo.png HTTP/1.1", upstream: "http://example/images/logo.png", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *263 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery-1.8.2.js HTTP/1.1", upstream: "http://example/javascripts/jquery-1.8.2.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *268 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.blockUI.js HTTP/1.1", upstream: "http://example/javascripts/jquery.blockUI.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *270 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.iframe-transport.js HTTP/1.1", upstream: "http://example/javascripts/jquery.iframe-transport.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *272 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.fileupload.js HTTP/1.1", upstream: "http://example/javascripts/jquery.fileupload.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *274 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.dropdownToggle.js HTTP/1.1", upstream: "http://example/javascripts/jquery.dropdownToggle.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:25 [error] 32291#32291: *276 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jscript.js HTTP/1.1", upstream: "http://example/javascripts/jscript.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *278 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/stylesheet.css HTTP/1.1", upstream: "http://example/stylesheets/stylesheet.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *280 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/stylesheets/jquery-ui.css HTTP/1.1", upstream: "http://example/stylesheets/jquery-ui.css", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *282 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/images/logo.png HTTP/1.1", upstream: "http://example/images/logo.png", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *284 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery-1.8.2.js HTTP/1.1", upstream: "http://example/javascripts/jquery-1.8.2.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *286 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.blockUI.js HTTP/1.1", upstream: "http://example/javascripts/jquery.blockUI.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *288 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.iframe-transport.js HTTP/1.1", upstream: "http://example/javascripts/jquery.iframe-transport.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *290 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.fileupload.js HTTP/1.1", upstream: "http://example/javascripts/jquery.fileupload.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *292 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jquery.dropdownToggle.js HTTP/1.1", upstream: "http://example/javascripts/jquery.dropdownToggle.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:08:26 [error] 32291#32291: *294 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /example/javascripts/jscript.js HTTP/1.1", upstream: "http://example/javascripts/jscript.js", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/onlyoffice/example/"
2020/11/25 18:32:59 [error] 6086#6086: *4471 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /6.0.2-5/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/info?t=1606325578631 HTTP/1.1", upstream: "http://127.0.0.1:8000/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/info", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/6.0.2-5/web-apps/apps/documenteditor/main/index.html?_dc=6.0.2-5&lang=en&customer=ONLYOFFICE&frameEditorId=iframeEditor&parentOrigin=https://onlyoffice.next.nohost.me"
2020/11/25 18:32:59 [error] 6086#6086: *4471 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: , request: "GET /6.0.2-5/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/info?t=1606325578631 HTTP/1.1", upstream: "http://[::1]:8000/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/info", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/6.0.2-5/web-apps/apps/documenteditor/main/index.html?_dc=6.0.2-5&lang=en&customer=ONLYOFFICE&frameEditorId=iframeEditor&parentOrigin=https://onlyoffice.next.nohost.me"
2020/11/25 18:33:01 [error] 6086#6086: *4475 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /6.0.2-5/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/info?t=1606325580701 HTTP/1.1", upstream: "http://docservice/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/info", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/6.0.2-5/web-apps/apps/documenteditor/main/index.html?_dc=6.0.2-5&lang=en&customer=ONLYOFFICE&frameEditorId=iframeEditor&parentOrigin=https://onlyoffice.next.nohost.me"
2020/11/25 18:33:06 [error] 6086#6086: *4483 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /6.0.2-5/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/472/tgbghesg/websocket HTTP/1.1", upstream: "http://docservice/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/472/tgbghesg/websocket", host: "onlyoffice.next.nohost.me"
2020/11/25 18:33:07 [error] 6086#6086: *4485 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "POST /6.0.2-5/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/472/h4mbtbc2/xhr?t=1606325586338 HTTP/1.1", upstream: "http://docservice/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/472/h4mbtbc2/xhr", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/6.0.2-5/web-apps/apps/documenteditor/main/index.html?_dc=6.0.2-5&lang=en&customer=ONLYOFFICE&frameEditorId=iframeEditor&parentOrigin=https://onlyoffice.next.nohost.me"
2020/11/25 18:33:07 [error] 6086#6086: *4487 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "GET /6.0.2-5/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/iframe.html HTTP/1.1", upstream: "http://docservice/doc/87.66.192.241__127.0.0.1https___onlyoffice.next.nohost.me_example_files_87.66.192.241__127.0.0.1_new.docx1606325511856/c/iframe.html", host: "onlyoffice.next.nohost.me", referrer: "https://onlyoffice.next.nohost.me/6.0.2-5/web-apps/apps/documenteditor/main/index.html?_dc=6.0.2-5&lang=en&customer=ONLYOFFICE&frameEditorId=iframeEditor&parentOrigin=https://onlyoffice.next.nohost.me"
Thanks for the help !