Calling API with bearer token not working

Question

I have an API which I can call locally using a bearer token and Postman.

I can also call the API on Azure, when authentication is switched off.

However, when I switch authentication on, try to call it with a token, I receive the following error:
"The page cannot be displayed because an internal server error has occurred."

The status in Postman says "500: Unable to download OpenID Connect Configuration"

I also tried adding the authorize attribute above one route on the controller, and created another route which just returns the string "hello"; I left this route open, not requiring authentication.
Again, I can access this without authentication locally, but as soon as it's deployed to Azure, I get this same error as above.

I suspect there is something I haven't set up correctly in Azure but I can't figure it out.
I'm also not seeing anything in App Insights. Not sure if I should be able to.

Any pointers will be greatly appreciated

Answer 1

I had the same issue when calling a function app. It was caused by the issuer URL being incorrect in the Authentication configuration. In my case it needed to be "<authentication-endpoint>/<tenant-id>/v2.0".