I had this issue after a couple months with my wired doorbell. All of a sudden nothing and I would see people walking past my place that should have triggered an event. I reset the doorbell via the app and it would last a week or so, but got to the point of resetting it every day. I finally contacted Eufy Support and after giving them tons of info and screen shots etc, they just sent me a full replacement. I got it installed yesterday and it’s working so far.
I would highly suggest everyone contact eufy support to let them know this isn’t an isolated incident that I had.