I'm having the same issue. Tried tapping mark all notifications read repeatedly, every time I got into a topic to read, they reappear. They do not show up on the see all notifications page.
The numbers keep alternating, slightly maddening.
I keep getting weird notifications too, like phantom upvote notifications. Usually they clear out, but sometimes they persist for a while.
I had two notifications that were popping up but not on the list. Logging out and logging back in seems to have gotten rid of them. You could try that?
The How To Advertise thread seems to be broken? Keeps giving me an internal error.
I had to hard refresh it (CTRL+R in Chrome) and it worked after that.
That did it.