I have an API that implements OAUTH Azure Active Directory Authentication. To achieve this, I created 2 App Registrations: Client and Backend.
I successfully implemented a Logic App able to call the API, so I am sure the authentication flow works.
Now, I need to call the same API from Power Apps, but unfortunately I got an error.
First, I create a Custom Connector

Then, I configure the Security section in this way:

- Client ID: it's the ID of the Client App Registration
- Client Secret: it's the secret of the Client App Registration
- Login Url: login Url from Microsoft
- Tenant Id: it's the Tenant Id of App Registrations
- Resource URL: I don't know what to put here, I tried by using the ID of the Backend App Registration
- Scope: It's not mandatory, but I tried to set the Application ID URI of the Backend App Registration concatenated to /.default.
When I try to create a Connection at the end of the wizard
I get this error
AADSTS650052: The app needs access to a service ("http://rts.powerapps.com") that your organization "a467080d-9919-4241-a48f-8b0002685a59" has not subscribed to or enabled. Contact your IT Admin to review the configuration of your service subscriptions.
My Client App Registration has the following API Permissions

UPDATE
Following @ChauncyZhou's suggestion and adding the Redirect URL generated by the Custom Connector to Client App Registration, I completed Custom Connector and Connection creation process.
When I test the API I get a 401 error:
The audience '97e**********************9c9' is invalid
Where 97e**********************9c9 is the Backend App Registration id. Did I make some mistake when I configured the Custom Connector? API works fine with Postman and Logic App.
