Preheating VOLVO Car app

Hello, I can’t (more) start the heater via APP. It worked until 1 week ago ALWAYS – on start and the car was warm. Now I always get the message “could not start”. I then filled – sometimes all errors in the ECUs deleted (was also nothing in the reference in it)…. no idea. When I then go to the car and start the heater over the display it starts immediately. Even if I start the car it always runs nicely with at first. Then I thought – ok, 5° is u. too warm – today it was 0° in the morning – the APP (and only the APP) doesn’t want – everything else works but over the APP. Does someone have an idea? Thanks uwe