Stopped working since updating from what? v31.0.1?
Can you fill out the actual support template? Your Nextcloud log, while reproducing the problem, may be relevant here.
Also, can you clarify which notifications you’re referring to specifically (i.e. some steps others can use to attempt to reproduce the problem)?
What do your Personal->Notifications and Administration->Activity settings look like?
Likely unrelated, but if you have a subdirectory installation then htaccess.RewriteBase should be adjusted to reflect that.