ron2112 said:

I think what might be happening is that you get one notification only until you visit the thread. After that you are notified of the next post, and then no more notifications until you visit the thread again. Which I guess is okay.

That's exactly what's happening. It used to send a notification for every reply, but then some people requested that it only send one notification until you view the thread.

I'll add a user setting so that you can choose how you want to be notified.