NC with Collabora Online - Built-in CODE Server (ARM64) on RockPro64

Hello there,
sorry if i ask a question answerd somewhere, but i did not found a solution for my problem.
I have Nextcloud 20.0.8 and Collabora Online - Built-in CODE Server (ARM64) 6.4.606 installed on a RockPro64. The OS is debian bullseye.

When i try to open a odt document i got the (german) error message “Collabora Online konnte nicht geladen werden - Bitte versuche es später noch einmal” means in english “Collabora Online could not be loaded - Please try again later” :thinking:.

I could not find a log file where i can determine more information about the problem.
Did i miss some configuration steps (e.g. at apache2)?
Everything else should be set up automatically during installation i think?

Trying to use the buildin “CODE Collabora Online Development Edition” on settings → Collabora Online shows “Es konnte keine Verbindung zum Collabora Online-Server hergestellt werden.” → english “No connection to Collaboration Online-Server possible.”

Using “https://DOMAINNAME:8443/apps/richdocumentscode_arm64/proxy.php?req=” on “use your own server” option did not work either.
As you see i use the port 8443 from external access to NC and redirect it on the firewall (FritzBox) to 443 on the interal RockPro64 system.

But it did not work either if i use the internal DOMANNAME (without port rerouting) :thinking:.

So my questions are - is the connection between NC and CODE an internal communication (so that i have to use the internal DOMAINNAME)?
And where and how did i get more logging information on NC to restrict the problem?

Many thanks for any information an help :smiley:.