title: Xamarin Forms: Token generating is not working when taking the update
body: <p>I have implemented the push notification feature for my xamarin forms project (both android and ios). The token registration class <code>FirebaseRegistrationService</code> is working only on the fresh installation. When taking updates this class is not firing and no token is generating. As per <a href="https://docs.microsoft.com/en-us/xamarin/android/data-cloud/google-messaging/remote-notifications-with-fcm?tabs=windows#implement-the-firebase-instance-id-service" rel="nofollow noreferrer">this</a> blog, <code>OnTokenRefresh</code> is invoked infrequently: it is used to update the token under the following circumstances:</p>
  <ul>
  <li><p>When the app is installed or uninstalled.</p>
  </li>
  <li><p>When the user deletes app data.</p>
  </li>
  <li><p>When the app erases the Instance ID.</p>
  </li>
  <li><p>When the security of the token has been compromised.</p>
  </li>
  </ul>
  <p>My problem is my app is already LIVE on the play store without the push notification. We have implemented the push notification now and planning to update it on play stores. But if the user takes the update the FCM registration will not work for them and they are not going to receive any notification. Existing users need to uninstall the app and install it again for getting the notifications. Is there any solution for this?</p>
  <p>But on the ios part, the <code>DidReceiveRegistrationToken</code> is invoking when taking updates, and no such token issue on the ios part.</p>