My guess is that it's a DNA problem...if it was a Verizon problem, we would be seeing more complaints.
hilmar2k, I think it depends on the cause. My notification was definitely on but was just not appearing. Apparently HenryKrinkle's phone's VM indicator was accidentally switched off.
Did you try a hard restart of the phone (not just turning it off but pulling restarting the phone)? I did that (I do that every few weeks, just to clear out the memory) and my notification popped up a few hours later.