Infinite loading screen, Collabora Nextcloud

PHP 7.4
Nextcloud 24.0.5
I tried to switch from OnlyOffice to Collabora, as the community document server of OnlyOffice has sooo many bugs.
I installed the Nextcloud Office app and the Collabora Online - Built-in CODE Server app. In the nextcloud settings page it shows that the server can be reached. But when trying to open a document, I´m getting an infinite loading screen and no error message.

Any ideas where I could even start looking for the problem?

error_log_apache tells this

[Wed Oct 05 11:29:10 2022] [error] [pid 23427] mod_proxy_fcgi.c(1006): (70007)The timeout specified has expired: [client] AH01075: Error dispatching request to : (polling)

take a look at this drawing and related threads:


You should have both Nextcloud and Collabora having valid DNS names (which is prerequisite for TLS). All this names should exist in DNS and be resolvable by each component - client Nextcloud server and Collabora must resolve all the DNS names to the right ip (your real server ip in this case as might be not the right one especially if you use some virtualization)