Using Classic Outlook on Windows for personal email, calendar, and contact management
I have the exact same problem with the notifications and this definitely happened after an Office update. I want to say it was at the same time MS did the major change to the search box in Outlook. So really the broke two things that worked fine in one update. I mean the search still works, but it is just now much less efficient.
Funny how this thread started in 2019 and there were MS reps all over it, and at that time I think it was actually user/machine issues with the notifications. Now that MS broke it we aren't hearing a peep out of them.