I noticed some guy before me has posted regarding the Me Tile not showing updates. This is similar but different. It still may be related but thought I'd start a new one because the interesting thing is this is happening to my wife's Lumia and both started at the same time.
Basically the Me Tile says 'x New Items' and when you go the notifications of the me tile there aren't any. The number can change once I actually get a new notification and then the me tile get's stuck with that number. Anyone else getting this?
Phone restart doesn't fix.
Haven't killed facebook account settings and recreated just yet. Want to wait this one out and see if it's server side issue and if both mine and my wife's start working correctly again.
I'm convinced that's what it is. My ME tile - and notifications in general - have been very slow to update, or haven't updated at all, or they display the same issue that you are facing. I find myself having to use the FB app to accurately check for FB updates. Twitter is the same, so I can't just be one of those platforms.