[pcdandy]

Late last year after an OS update, notifications in macOS mysteriously stopped popping up. They were getting triggered and could be seen by opening the right sidebar, but the banners were no longer popping up in the corner anymore. I had been using them to remind me of any upcoming meetings in my employer's Google calendar, so when they stopped appearing, I suddenly found myself unintentionally missing those meetings altogether. (I found a workaround by using Slack's Google calendar integration to send me reminders there.)

Well, turned out that although the Focus -> Do Not Disturb settings had been disabled, the settings were behaving as though they were enabled anyway! It was set to only allow certain apps to show banners. Only when I changed this setting (a few months later nevertheless) did notification banners finally start working properly as before. Perhaps I ran into an extreme edge case that the Apple engineers overlooked somehow, but it does make me wonder whether they are doing anything at all to identify and cover such edge cases.

[pcdandy]

edit: Looked further, found that the cause ultimately turned out to be the 'Allow notifications when mirroring or sharing the display' setting under Notifications, which was off by default. I use an external monitor almost the entire time but I would expect that setting to be on by default, at the very least.