[member='Norin Terrek']
I don't have all the answers, however you should check to see if you unclicked the notifications for mentions.
Go to Settings > Notification Options
Check if "Notify me when someone mentions me in a post" is ticked under Notification List.
I also suggest using the "Follow this Topic" function each thread has, it can be found at the top beside the Topic Title, and it will provide you with further notifications each time somebody responds to that thread. Very useful for roleplays, character sheets, submissions, etc. It won't fail, whereas the Mention feature is known to be buggy.
EDIT:
I'd also recommend asking an Admin if you have a space at the beginning or end of your name. This can mess up the Mention button.