title: Xamarin Forms Plugin.Share not working for unknown reason
body: <p>We have an image with a gesture recognizer, which calls the CrossShare.Current.Share method. On Android this works fine but on iOS it does not. No error is thrown and there doesn't seem to be any issues, but the share sheet does not appear and from the user's point of view nothing happens when you click the button.</p>
  
  <p>Have I missed some permissions or something somewhere?</p>
  
  <p>This is my method;</p>
  
  <pre><code>async void On_Share(object sender, EventArgs e)
  {
      if (CrossConnectivity.Current.IsConnected)
      {
          var message = "Check out this";
          var title = "Share this";
          await CrossShare.Current.Share(new ShareMessage { Text = message, Title = title}, new ShareOptions { ExcludedUIActivityTypes = new[] { ShareUIActivityType.PostToFacebook } });
      }
      else
      {
           NoInternetLabel.IsVisible = true;
      }
  }
  </code></pre>
  
  <p>It doesn't throw any errors and I can step through the method fine - it definitely hits the Share line. This problem is only showing on iOS, Android has no issues.</p>
  
  <p>EDIT: Seems to be working fine (we've tried doing it natively as well - without plugin) but now I'm getting Warning: Attempt to present on  whose view is not in the window hierarchy!</p>