Certificate installation failed: SEC ERROR REUSED ISSUER AND SERIAL

I bought a olimex LIME2 and installed yunohost on it.

I’m getting this error when I want to visit the yunohost admin.

Secure Connection Failed

An error occurred during a connection to You have received an invalid certificate. Please contact the server administrator or email correspondent and give them the following information: Your certificate contains the same serial number as another certificate issued by the certificate authority. Please get a new certificate containing a unique serial number. Error code: SEC_ERROR_REUSED_ISSUER_AND_SERIAL

    The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
    Please contact the website owners to inform them of this problem.

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Apperently something went wrong with trying to install the certificate.
This is what happens when I retry installing the certificate.

admin@Gildurklaus:/etc/nginx/conf.d/guilder-test.eu.org.d$ sudo yunohost domain cert-install --no-checks guilder-test.eu.org --debug
416  DEBUG loading actions map namespace 'yunohost'
526  DEBUG extra parameter classes loaded: ['ask', 'password', 'required', 'pattern']
528  DEBUG initializing base actions map parser for cli
534  DEBUG registering new callback action 'yunohost.utils.packages.ynh_packages_version' to ['-v', '--version']
805  DEBUG unable to load locale 'en' from '/usr/share/moulinette/locale'
807  DEBUG unable to load locale 'en' from '/usr/lib/moulinette/yunohost/locales'
906  DEBUG initialize authenticator 'ldap-anonymous' with: uri='ldap://localhost:389', base_dn='dc=yunohost,dc=org', user_rdn='None'
916  DEBUG lock has been acquired
6502 INFO processing action [1783.1]: yunohost.domain.cert-install with args={'no_checks': True, 'force': False, 'domain_list': ['guilder-test.eu.org'], 'self_signed': False, 'auth': <moulinette.authenticators.ldap.Authenticator object at 0xb67e2750>, 'staging': False}
7273 INFO Now attempting install of certificate for domain guilder-test.eu.org!
7278 INFO Adding Nginx configuration file for Acme challenge for domain guilder-test.eu.org.
7381 DEBUG Running 'systemctl reload nginx'
7634 SUCCESS The SSOwat configuration has been generated
7638 DEBUG Making sure tmp folders exists...
7975 INFO Prepare key and certificate signing request (CSR) for guilder-test.eu.org...
22158 INFO Saving to /tmp/acme-challenge-private/guilder-test.eu.org.csr.
22162 INFO Now using ACME Tiny to sign the certificate...
22163 INFO Parsing account key...
22225 INFO Parsing CSR...
22276 INFO Registering account...
24801 INFO Already registered!
24803 INFO Verifying guilder-test.eu.org...
26652 ERROR Wrote file to /tmp/acme-challenge-public/WA5u5u5h_pa4GJqYlu4A1tuwYunx2Ba0W99YFC2lz6k, but couldn't download http://guilder-test.eu.org/.well-known/acme-challenge/WA5u5u5h_pa4GJqYlu4A1tuwYunx2Ba0W99YFC2lz6k
26654 ERROR Certificate installation for guilder-test.eu.org failed !
Exception: [Errno 22] Signing the new certificate failed
26656 DEBUG action [1783.1] ended after 20.151s
26657 DEBUG lock has been released