Having the exact same issue. It’s only a month old and after successful install, it worked first day, but then it lost wifi connection and I could not get it back on. Put it away for several days and connected it againt today, then it found Wifi, and was working for an hour or so, then lost connection and cannot enter setup mode, even after a hard reset (30s). Nothing happens when pushing the setup button once. I use the transformer shipping with the product as I do not have an existing door bell or transformer in my house. The output voltage of the transformer is 30V AC between 1-4, and 18V AC between 1-3. I tried both. Last health status was 4025mvV and working.
See this video for me connecting it to power, trying entering setup mode and measuring voltage: https://youtu.be/ASEB-xdf-sk