Webmail not working after upgrade to v65


I’ve just upgraded to v65. It first died with an error regarding munin

[FATAL ERROR] Lock already exists: /var/run/munin/munin-update.lock. Dying.
at /usr/share/perl5/Munin/Master/Update.pm line 129.

but it succeded after the second try.

When I try to open the webmail client /mail/ or the cloud /cloud/, I just get the text error message “File not found” in the browser. Not more, not less.
When I look into the /var/log/nginx/error.log file, I see this error message:

2023/11/20 12:25:13 [error] 62449#62449: *4 FastCGI sent in stderr: “Primary script unknown” while reading response header from upstream, client: xx.xxx.xxx.xxx, server: box.somehost.de, request: “GET /mail/ HTTP/2.0”, upstream: “fastcgi://unix:/var/run/php/php8.0-fpm.sock:”, host: “box.somehost.de

Can someone tell me whats going on? This was working the last time I checked it.

Thanks for your help!

BTW: I rerun the upgrade, ran the sudo mailinabox command a couple of times and rebooted the server. All system status checks are green.