title: FCM notification doesn't show notification pop up in background
body: <p>I'm using firebase cloud function for showing notification in my app and that working perfectly only issue I'm facing is when app is closed or in background notification doesn't show pop up.
  Heads up notifications are used in app and I do get the notification but notification doesn't pop up as it do while app is in foreground.I have set the Priority to high for both channel and notification but still it doesn't work.</p>
  <p>My Service Class :</p>
  <pre><code>@Override
      public void onMessageReceived(RemoteMessage remoteMessage) {
          super.onMessageReceived(remoteMessage);
          Log.d(&quot;msg&quot;, &quot;onMessageReceived: &quot; + remoteMessage.getData().get(&quot;message&quot;));
          Intent intent = new Intent(this, WebViewActivity.class);
          intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
          PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);
          String channelId = &quot;Default&quot;;
          NotificationCompat.Builder builder = new  NotificationCompat.Builder(this, channelId)
                  .setSmallIcon(R.drawable.app_logo)
                  .setContentTitle(remoteMessage.getNotification().getTitle())
                  .setContentText(remoteMessage.getNotification().getBody())
                  .setAutoCancel(true).setContentIntent(pendingIntent)
                  .setDefaults(DEFAULT_SOUND | DEFAULT_VIBRATE)
                  .setPriority(Notification.PRIORITY_MAX);
          NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
          if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.O) {
              NotificationChannel channel = new NotificationChannel(channelId, &quot;Default channel&quot;, NotificationManager.IMPORTANCE_HIGH);
              channel.setShowBadge(true);
               channel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);
              manager.createNotificationChannel(channel);
          }
          manager.notify(0, builder.build());
      }
  </code></pre>
  <p>Manifest</p>
  <pre><code>&lt;application
          android:allowBackup=&quot;true&quot;
          android:icon=&quot;@mipmap/ic_launcher&quot;
          android:label=&quot;@string/app_name&quot;
          android:roundIcon=&quot;@mipmap/ic_launcher_round&quot;
          android:supportsRtl=&quot;true&quot;
          android:theme=&quot;@style/AppTheme&quot;&gt;
  
          &lt;activity android:name=&quot;com.noderon.riscalert.WebViewActivity&quot;&gt;
              &lt;intent-filter&gt;
                  &lt;action android:name=&quot;android.intent.action.MAIN&quot; /&gt;
  
                  &lt;category android:name=&quot;android.intent.category.LAUNCHER&quot; /&gt;
              &lt;/intent-filter&gt;
          &lt;/activity&gt;
          &lt;activity android:name=&quot;com.noderon.riscalert.MainActivity&quot;&gt;
  
          &lt;/activity&gt;
  
          &lt;service
              android:name=&quot;.NotificationService&quot;&gt;
              &lt;intent-filter&gt;
                  &lt;action android:name=&quot;com.google.firebase.MESSAGING_EVENT&quot;/&gt;
              &lt;/intent-filter&gt;
          &lt;/service&gt;
  
      &lt;/application&gt;
  </code></pre>
  <p>Any help would be appreciated. Thanku</p>