I'm not to familiar with this particular forumsoftware.
Your "problem" might be the fact that you have chosen to get "instant email notification" rather than "daily email notification".
In other forums I've learned that "instant email notification" will notify me once upon the first post to the thread.
I will then not receive any more notifications until I've been logged on to the forum.
"daily email notification" will send me a complete list of all post to the subscribed thread for the past 24 hours by email just past midnight every night. Regardless if I've been logged in or not.
Svein Olav, Norway
1977 BMW R75/7 awaiting restoration
1995 Suzuki TU250 Volty
1995 BMW F650