solved_Seafile 9.0.4 "Add User" failed

Hello Greetings from Germany,

Im using Seafile 9.0.4 CE on a Proxmox–Ubuntu 18.04 LXC Container.
I am running this Setup since Years. Starting on Ubuntu 16.04 and Seafile 6.
I have upgraded OS and Seafile several Times.

Now my Web-Gui seems to work not properly anymore.

After Login to the Web-Gui I am klicking the Button “About” and nothing happens.
In “System Administration” / “Users” the Buttons “Add User” and “Import User”
also dont work. "Export to xls" works.
“Add Group” is not working.
But I can edit existing Users.

Here is what I have done so far:

Sart / Stop “seafile.service”
Run “”
check Permissions @ “/opt/seafile”
Reboot LXC Container.

No Succes.

I have stumbeld around in “/opt/seafile"logs” try to find the Error
But I don’t understand everything that is in these files.

Maybe someone of you can help me?

After disableing an old Custom css (httxs:// the system works fine.
Now i am using httxs://