RADIUS Authentication works but not Accounting

You can temporarily enable debugging to see what is exactly happening that causes the session to be rejected.

In the logging profile associated to your access profile change the log level to debugging for Access Policy logs.

To see the debug logs for a specific session : overview > Access reports and run the All Sessions report (the default one), you'll probably get a hundreds debugging lines (you can search for terms like denied or fallback).

Don't forget to rollback the logging level to avoid unnecessary logs.