Server 5.11 Profile Manager Admin Site blank/empty
After upgrading Server 5.10 on Catalina to BigSur 11.1 and Server 5.11:
Profile Manager was running as usual, after 3 weeks suddenly the profile manager admin site is not accessible. When calling the server in any browser, the selection between MyDevices and ProfileManager is visible. MyDevices page is working. Profile Manager is asking for login, after filling credentials and sending login only blank page is shown. Sometimes after some time a message is shown „network error“, sometimes nothing happens. In browser console error regarding javascript-packed is shown.
In browsers the correct SSL certificate is shown.
In server logs I see all devices communicate with the MDM.
In Server app reachability for Profile Manager ok, PM running. Button MyDevices working. Button ProfileManager leading to blank page.
Did reinstall MacOS, deleted Server app and reinstalled it several times.
Any help or hint appreciated.