Go to the board/section you want to get notifications for each new topic. In the right side, find out notify and click on it. You will get a pop up message. Click ok on it. I have attached image below.

If you are still missing notifications, check your spam folder. That's what I got by digging a little. Check this thread. It's worthy to have a look- https://bitcointalk.org/index.php?topic=212818.0;prev_next=next