I experienced this problem with a teacher's iPad today. It was unusual because the device was working perfectly with Apple Classroom yesterday. The issue was not school wide but specific to one teacher. The teacher's device is on iOS version 15.1.
After attempting many things on both Apple School Manager and the Workspace ONE UEM console I stumbled upon quite a simple solution. On the iPad I opened the Hub application, clicked "This Device" and then clicked "Send Data". This resolved the issue.
Hope this helps. Good luck.