Please see the list of Common Problems if something is not working as you expect it. This page describes how to create and access the logs if you need more information about what's happening behind the scenes.
Check Azure Web App log files via Advanced Tools:
Go to Kudu
Navigate to LogFiles
Click on the download icon on the latest .txt file and review it
Configure the App Services Logs
Check the Log Stream of the App Service.
Monitor the log stream
Reproduce the error
Look for the log starting with Request validation unsuccessful, as Intune validation threw an exception
These message should have more details