I have the same issue - motion notifications don’t work, but in my case it’s when Cam Plus is assigned to the camera. For me the only way to get motion notifications to work is to turn off Cam Plus completely. Turning off notifications for AI events and leaving motion events on was not sufficient to make it work.
It has been broken this way for at least a month, which is when I wanted this functionality. I reported it to support just now, will see how long it takes to fix it.