There were problems with notifications last week, but everything should work fine now. I can confirm that I'm getting the notifications on the thing I follow.
What still hasn't been fixed are the weekly and daily digests: https://answers.dynatrace.com/articles/226964/daily-and-weekly-digests-are-temporarily-disabled.html
@sebastian k. - you're right. There were three notification outages in the last 6 months. Definitely too many as we know how much our users rely on notifications on the tags or forums they follow.