I have the same issue, notifications stopped overnight a few days ago (12th Oct). Figured I’d give it a few days for them to look into it. I don’t subscribe to an online plan, just record locally on an SD card, although that’s problematic at times but I won’t moan about that now.
Anyway, I’ve just noticed the motion detection for both cameras is turned off so it might be worth checking yours too - I’d focused on the general settings rather than double checking motion detection (as it was turned on). The android app isn’t set to auto update and I’m still running v5.16.2 because I’d heard newer updates have caused problems, so not sure why this setting suddenly decided to turn itself off during the night (presume it’s a firmware update or something - now on 1634). It’s back on now and I’ve just received a notification for both cameras as I walked around the house (and the cat has just set it off too), so fingers crossed it continues to work and you’re able to sort out yours too.