Works fine with app when i am local. Away about 100 miles for weekend off lone whole time. Cam back home and works again???.
This sounds like your phone doesn’t have a reliable internet connection while on the mobile data.
See if you have a link while away but on WiFi connection.
Odd my other remote lighting app worked fine and i got an alert that the door was opened and closed by my daughter. All this when i was away.
The connection might have been intermittent. Next time you can also try web app. It reports even is a single request times out.