You may pass the client ID value for the ‘resource’ as mentioned in this similar
discussion thread, and see if that makes any difference.
In addition, you could use Fiddler to catch some error message to isolate any specific issues.
Furthermore, if you enable application
logging, you will see authentication and authorization traces directly in your log files. If you enable ‘failed request
tracing’, you can see exactly what role the authentication and authorization module may have played in a failed request. In the trace logs, look for references to a module named EasyAuthModule_32/64.
Checkout the suggestions outlined in this document
Authentication and authorization in Azure App Service for more details on this topic.
Reference:
POSTMAN: “You do not have permission to view this directory or page”