I have a function app in Azure and one of the functions is GetId. Now i call this via the following:

  https://<function_name>.azurewebsites.net/GetId?firstname=bob&surname=builder

Now i get a token from Azure via an app registration and use that to call the endpoint.
The error i get is

     "500 Internal server error" or
     "Forbidden"  (when i run from VS locally)

Should i create a new app registration and retry ?
How can i see what the error is or get it working ?