title: Window prompt not showing when using MSAL .NET library in Unity3D
body: <p>I'm trying to log in to SharePoint with my Unity app via the MSAL library (Microsoft Identity Platform). When I run it the first time I don’t see a popup at all and there are no errors. (note, I've tried in Editor and as a standalone exe)</p>
  
  <p>However, I did notice after running a second time, I get a popup window entitled <code>Oops</code> with the message <code>Could not register the window class win32 error 0</code>.  After some googling I think it might be because there is some kind of dangling window in the background somewhere after the first attempt that I need to somehow clean up. If I restart Unity I can run again with the first time having no error but again no popup window. If I run a second time, of course, I again get the <code>Oops</code> message. </p>
  
  <p>Probably unrelated but worth noting is that if I hit “Ok” on the <code>Oops</code> window I get a null exception error. It seems the AcquireTokenInteractive is trying to open a window which fails, leaving it null, and then tries to get the token from the null. </p>
  
  <p>Any advice to help figure out why the window isn’t presenting would be greatly appreciated</p>
  
  <pre class="lang-cs prettyprint-override"><code>using Microsoft.Identity.Client;
  
  public class MyApp: MonoBehaviour
  {
      private string ClientId = "i-am-not-telling";
      private string Tenant = "common";
  
      void Start()
      {
          SharepointLogin();
      }
  
      public async void SharepointLogin()
      {
          PublicClientApp = PublicClientApplicationBuilder.Create(ClientId)
                  .WithRedirectUri("https://login.microsoftonline.com/common/oauth2/nativeclient")
                  .WithAuthority(AzureCloudInstance.AzurePublic, Tenant)
                  .Build();
          IEnumerable&lt;string&gt; scopes = new List&lt;string&gt; { "User.Read" };
          AuthenticationResult result;
          result = await PublicClientApp.AcquireTokenInteractive(scopes)
                          .ExecuteAsync();
      }
  }
  
  </code></pre>