Access_token returning null from msal

I am making a call to Azure B2C that appears to be successful.  I am getting an id_token but not an access_token that I can use to a latter call to api's and mobileservices.  

I am writing a mobile app using xamarin with the microsoft.identity.client package.  Some help in pointing me in the right direction for getting an access_token returned would be appreciated.

Thanks

app.xaml.cs

              public static IPublicClientApplication AuthenticationClient { get; private set; }
                        public static object UIParent { get; set; } = null;
                        public App()
                        {
                            InitializeComponent();
                            AuthenticationClient = PublicClientApplicationBuilder.Create(Constants.ClientId)
                                .WithIosKeychainSecurityGroup(Constants.IosKeychainSecurityGroups)
                                .WithB2CAuthority(Constants.AuthoritySignin)
                                //.WithRedirectUri($"msal{Constants.ClientId }://auth")
                                .Build();
                            MainPage = new AppShell();
                        }

Page that displays a button that calls loginasync

settings.xaml.cs

                  async void OnLoginButtonClicked(object sender, EventArgs e)
                    {
                        AuthenticationResult result;
                        IEnumerable<IAccount> accounts;
                        try
                        {
                            System.Diagnostics.Debug.Write("before await get tokken");
                        result = await App.AuthenticationClient
                        .AcquireTokenInteractive(Constants.Scopes)
                        .WithPrompt(Prompt.SelectAccount)
                        .WithParentActivityOrWindow(App.UIParent)
                        .WithUseEmbeddedWebView(true) // this line was not in the sample, had to add to get to work on android without chrome installed
                        .ExecuteAsync();
                    JObject objToken = new JObject();
                    objToken.Add("access_token", result.AccessToken);
                    System.Diagnostics.Debug.WriteLine("access_token:", objToken.ToString());
// Access_token at this point is null, idToken has a value.

                
                MobileServiceUser user = await MobileService.LoginAsync(MobileServiceAuthenticationProvider.WindowsAzureActiveDirectory , objToken);


                accounts = await App.AuthenticationClient.GetAccountsAsync();
                //var account = GetUserData(result.AccessToken);
                //await Navigation.PushAsync(new LogoutPage(result));
            }
            catch (MsalException ex)
            {
                if (ex.Message != null && ex.Message.Contains("AADB2C90118"))
                {
                    //result = await OnForgotPassword();
                    //await Navigation.PushAsync(new LogoutPage(result));
                }
                    else if (ex.ErrorCode != "authentication_canceled")
                    {
                            await DisplayAlert("An error has occurred", "Exception message: " + ex.Message, "Dismiss");
                        }
                    }
                }

constants.cs

            public static class Constants
            {
                // set to a unique value for your app, such as your bundle identifier. Used on iOS to share keychain access.
                static readonly string iosKeychainSecurityGroup = "com.xxxnextbook.mynextbook";
                public static string ApplicationURL = @"https://xxxnextbookwebapp.azurewebsites.net";
                static readonly string tenantName = "xxxNextBook";
                static readonly string tenantId = "xxxNextbook.onmicrosoft.com";
                static readonly string clientId = "xxxxxxxx-72df-45e3-a84b-717317ec75c3";
                static readonly string policySignin = "B2C_1_xxxNextBookSignIn";
                static readonly string policyPassword = "B2C_1_xxxNextBookPasswordReset";
                // The following fields and properties should not need to be changed
                static readonly string[] scopes = { "https://xxxxNextbook.onmicrosoft.com/xxxNextBook/read" };
                static readonly string authorityBase = $"https://{tenantName}.b2clogin.com/tfp/{tenantId}/";
    ....
    }

Brady Brady@acm.org