Can't connect to Built-in CODE Server in Nextcloud

hey there,

I’m trying to set up Collabora in Nextcloud. I’m currently running Nextcloud 22.1.1, but it was also not working on a prior version. I installed Collabora and the Built-in CODE Server from the Nextcloud AppStore, but the connection doesn’t work. My Nextcloud instance is managed by a big cloud-hoster, so I’m not able to configure anything that’s not accessible in the GUI.
Using a demo-server is working fine, but that’s no solution.

Does anyone have an idea?