Office 365 Connector and sso

I set up a UCS4.4 and configured Letsencrypt for the certificate (dc01.mydomain.ch and ucs-sso.mydomain.ch), which works fine. Danch Office 365 Connector installed and configured, works fine. If I want to log in to the O365 I will be redirected to the URL “https://ucs-sso.schule-gebenstorf.ch/simplesamlphp/saml2/idp/SSOService.php”, but simple samlphp doesn’t work or can’t be reached. The following error message appears:

Not Found

The requested URL was not found on this server.
Apache/2.4.25 (Univention) Server at ucs-sso.schule-gebenstorf.ch Port 443

I don’t know anymore, is the Letsencrypt certificate missing the 2nd hostname?

Many thanks for the help