Fixes https://github.com/MicrosoftDocs/xamarin-docs/issues/3065

Author: davidbritch

WebServices/AzureNotificationHub/README.md

@@ -13,7 +13,8 @@ urlFragment: webservices-azurenotificationhub
 
 This sample demonstrates how to use Azure Notification Hubs to send push notifications to Xamarin Forms applications on Android and iOS.
 
+On iOS 13 and greater, you may experience intermittent device registration issues if your app is running over a wireless network, rather than a cellular network. For more information, and a workaround, see [iOS-13 Unable to receive Device Token](https://developer.apple.com/forums/thread/128172) on developer.apple.com.
+
 To run the Android application, you must replace the google-services.json file with a file downloaded from your Firebase console.
 
 For more information about this sample see [Push notifications with Azure Notification Hub and Xamarin Forms](https://docs.microsoft.com/xamarin/xamarin-forms/data-cloud/push-notifications/azure-notification-hub).
-