I've had this working fine for 4 years. Last night the Thermostat wouldn't connect to the Heat link anymore. So I tried a manual reset of the thermostat (i.e. held the screen for 10 seconds).
From the app, when I try "Add product", scan the thermostat QR code, it says "Connecting to your thermostat", then "Looking for Wifi networks" and lists my network. Before I can type in the password though, it seems to time out and says "Something went wrong. We're having trouble finding a Wi-Fi network. TD004 (4060)".
I've tried multiple times and on different phones (I read about others having problems with Pixel 6a, so tried my wife's Samsung A41). We haven't recently changed the wifi network or my phone.