Just go to Apps in settings in Android.
Find fitbit there and click it.
And click clear data/storage for fitbit app.
Done.
Now you have to login to your fitbit app again and your notification service will be running.
of course, your previously saved auto replies will be deleted. but there is no option.
But notification services will work definitely.
You have to do it every time the notification service is not running. It happens nearly once in one week for me.
