microsoft-authentication-library-for-dotnet: Moving from login.microsoftonline.com to b2clogin.com causes `The IDP client key/secret is not properly configured` error with Facebook IDP

I upgraded to MSAL 2.7.0 and tried to move to <tenant>.b2conline.com I am using Xamarin Forms

In my Xamarin Forms application, the login screen appears, I am able to register and also get my user created but the control never gets redirected to my app. (the application just hangs). Am I missing a redirect setting somewhere ? In my native app; I set my redirect to msal<tenantid>😕/auth

What authentication flow has the issue? Native/Xamarin

Other? - please describe;

Repro

  AuthenticationClient = new PublicClientApplication(AppSettings.B2cClientId,
                $"{AppSettings.B2cAuthority}{AppSettings.B2cTenant}/{AppSettings.B2cPolicy}");
            AuthenticationClient.RedirectUri = $"msal{AppSettings.B2cClientId}://auth";
…

                var result = await App.AuthenticationClient.AcquireTokenAsync(
                    AppSettings.Scopes,
                    GetAccountByPolicy(accounts, AppSettings.DefaultB2cPolicy), 
                    App.UiParent);

Hangs in the above line.

Expected behavior I was expecting it to return with the access tokens so that I can save them and move to the next screen.

Actual behavior The application just freezes