Vikunja, no login possible / no user exist after install

Hello!

My YunoHost server

Hardware: VPS (Hetzner)
YunoHost version: 11.2.9.1 (stable)
I have access to my server : Through Hetzner Root Shell
Are you in a special context or did you perform some particular tweaking on your YunoHost instance ? : no

Description of my issue

I install Vikunja under a new sub-domain. LetsEncrypt was successfully. Some other apps are still installed and work well.

I test with a standard user or admin: logged in to dashboard, click on Vikunja Icon and it shows my V. Subdomain without errors. I see the login prompt of V. I tried with standard logins or admin, but no success. → wrong name or password

Logs

in /var/log/ i cant see V. log files

Thanks

You have to register a user first before you can log in, if I remember correctly … There is no admin in that sense.