How to resolve the issue "Unable to resolve app registration name from registered app ID" under Function App

Paul 15

I have been following this guide to create a web app.

https://learn.microsoft.com/en-us/azure/api-management/howto-protect-backend-frontend-azuread-b2c

I have no issues creating a B2C tenant, the backend / frontend applications, and the user flow.

All have been created successfully under AD B2C.

Next, I created a Function App under my main account. When I'm add a "Microsoft Identity Provider" Under Authentication of the Function App, I encountered the error "Unable to resolve app registration name from registered application ID". My question is: is there any setting I may have missed in configuring the link between the B2C tenant to my main subscription tenant? Any policies / authentication steps I may have missed?

User's image

When creating the Microsoft Identity Provider, here's where I have found the information:

application (client) ID: I obtained this value from the backend application created under B2C
client secret value: the secret value after creating a secret ID and value pair under "Certificates and Secrets" under the same web app in B2C
Issuer URL: the URL as appear at the top after clicking on the "run user flow" in the User Flow page under the same web app in B2C

JamesTran-MSFT 36,361 Reputation points Microsoft Employee

2023-02-10T18:01:42.1666667+00:00

@Paul

Thank you for your post and I apologize for the delayed response. My team is currently looking into this issue and will update as soon as possible.
Khurram Rahim 1,841 Reputation points

2023-02-17T05:07:53.7+00:00
To resolve the error "Unable to resolve app registration name from registered application ID," you may have missed a few configuration steps between your B2C tenant and your main subscription tenant.

Verify that you have granted the correct permissions to your Function App in your B2C tenant. Go to the Azure portal, and navigate to the App registrations section of your B2C tenant. Find the application you created, and then go to API permissions. Ensure that the necessary permissions have been granted to the Function App.

Check if you have correctly configured the "Microsoft identity provider" settings in your Function App. Ensure that the "Client ID" value is the same as the Application (client) ID of your backend application in B2C. Ensure that the "Client secret" value is the same as the client secret value for the same backend application in B2C. The "Issuer URL" should be the URL as shown at the top after clicking on the "Run user flow" in the User Flow page under the same web app in B2C.

Finally, make sure that you have added the Function App to the list of "Reply URLs" in your backend application in B2C. Go to the "Reply URLs" section in the app registration for your backend application in B2C and add the URL for your Function App.

By verifying these steps, you should be able to resolve the error and successfully link your B2C tenant to your main subscription tenant.
Ross Attrill 0 Reputation points

2024-01-15T08:45:30.7366667+00:00

Thank you Khurram for this detailed response. I am having exactly this problem and am trying to follow your instructions but have the following difficulties:

At your step 1, when I am unable to grant permission to the function app. It seems necessary that the B2C tenant is in a different directory to the function app. However, when trying to add API permissions to the B2C app, it doesn't seem possible to add an API in another directory. There are 3 options - 'Microsoft APIs' which includes Graph, 'APIs my organization uses' which only includes APIs in the same directory as the B2C tenant and 'My APIs' which also doesn't see the function app or allow anything to be added.

At your step 3, I just can't see where to add a Reply URL in an app registration in the portal.
Nam Do 0 Reputation points

2024-03-01T08:17:52.9433333+00:00

@Ross Attrill Hi Ross, were you able to find a solution to this issue? Thank you!
Nam Do 0 Reputation points

2024-03-01T08:20:22.6333333+00:00

Hi @Ross Attrill - were you able to find a solution to this issue? Thank you!