title: Firebase notifications not showing up in my emulator
body: <p>I am trying use Firebase to display a notification in an emulator.  The notification appears in the logcat view, but, the emulator displays a message "Failed to post Notification on Channel notify_001"
  The referenced issue did not work for me.  I posted a new question so my exact code code be listed.
  My SDK 
  compileSdkVersion 26
  minSdkVersion 18
  targetSdkVersion 26</p>
  
  <p>Code:</p>
  
  <pre><code>public class MyAndroidFirebaseMsgService extends FirebaseMessagingService {
      private static final String TAG = "MyAndroidFCMService";
      @Override
      public void onMessageReceived(RemoteMessage remoteMessage) {
          //Log data to Log Cat
          Log.d(TAG, "From: " + remoteMessage.getFrom());
          Log.d(TAG, "Notification Message Body: " + remoteMessage.getNotification().getBody());
          Log.i(TAG, "instance id " + FirebaseInstanceId.getInstance().getId());
          //create notification
          createNotification(remoteMessage.getNotification().getBody());
      }
  
      private void createNotification( String messageBody) {
          Intent intent = new Intent( this , ResultActivity. class );
          intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
          PendingIntent resultIntent = PendingIntent.getActivity( this , 0, intent,
                  PendingIntent.FLAG_ONE_SHOT);
  
          Uri notificationSoundURI = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
          NotificationCompat.Builder mNotificationBuilder = new NotificationCompat.Builder
                  ( this, "Notify_001")
                  .setSmallIcon(R.mipmap.ic_launcher)
                  .setContentTitle("Android Tutorial Point FCM Tutorial")
                  .setContentText(messageBody)
                  .setAutoCancel( true )
                  .setSound(notificationSoundURI)
                  .setContentIntent(resultIntent);
  
          NotificationManager notificationManager =
                  (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
  
          if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.O) {
              NotificationChannel channel = new NotificationChannel("notify_001",
                      "Channel human readable title",
                      NotificationManager.IMPORTANCE_DEFAULT);
              notificationManager.createNotificationChannel(channel);
          }
  
          notificationManager.notify(0, mNotificationBuilder.build());
      }
  }
  </code></pre>