Error when entering a Meeting room

I have successfully installed a Jitsi installation on a server (Ubuntu 20.04, 6 cores, 64GB RAM, 1TB disk space) at Keyweb Hoster.
I can also access the start page directly. However, as soon as I enter a meeting room, whether existing or newly created, I get an error message “Unfortunately, something went wrong.
We are trying to fix it. Connect in 17 seconds”
I have no idea what this error is, so the question, where can I find the corresponding logfile on the server?
Where can I start looking? TCP ports 22/80/443 and UDP ports 10000:20000 are allowed in both directions.
Thanks for the support.
BR Mercy

Welcome to the forum.

Check out this post for where to access logs and config files - [TIP] Fastest Way To Get Support In The Forum