Hi Daniel,

It's a combination of settings that you must have turned on.

First of all, you need to make sure you have selected the option "Turn reply notifications on" that shows-up on the right hand-side of the screen, in a thread.

Afterwards, to make sure you receive an email notification about this, you must check your profile settings by going to the "Email Digest" tab in your profile settings, and  in the "Frequency" tab, select the option that fits best for you from the three: Not subscribed, Daily, Weekly. 

This will determine how many times you get email notifications.

To double check that you are subscribed to a forum and you will get the notifications, you can check in the "Subscriptions" tab if you are subscribed to that particular forum.

However, please note that this is to double check the forum area, overall.

To double check that you will get notifications based on the initial option "Turn reply notifications on", you must also check the "Notifications" tab in the settings, and make sure you have selected the "Email" option for activity from your subscriptions, such as "Replies to a thread I'm subscribed to".

Therefore, I'd advise for you to do a double-checking of all these options in your profile settings and see, maybe you need to activate/reactivate some options.

Let me know if you still need assistance afterwards.

All the best,
Georgiana