while i can't directly give you the solution but you can try to find the exception or error messages from linux app service using one of the below methods:

1. go to web app -> monitoring -> log stream, see if the console providing an error output.

2. install VS Code, install azure app service extension. sign in your azure account, browse to your linux web app, finally try to access raw system log as shown in the screenshot. I found I have more success rate finding raw exception this way.