There's a bug, fixed in 2.2.1, where the widget would show "No Players" when the notification was not showing (along with a few in-between cases).

Starting with 2.2.0, timely widget updates are tied to the presence of the notification. If you swipe away the notification (or on Android 4.x, hit the X button) then you are killing the server connection and the widget will no longer updated immediately. It will be updated per a typical Android widget update interval, 30 minutes. Not terribly useful though.

The notification has a purpose. It serves to let you know that your device has a background service running, and is actually 100% mandatory in Android 8.0 anyways to prevent your service from being killed very quickly. If you strongly dislike the notification, then on most modern devices you can choose to hide notifications from specific apps.

FTR, tested here on Android 4.4, 5.1, 7.0 and 8.0.

I'm going to start a new thread for 2.2.x to pull things together. Maybe move the discussion over there.