Please troubleshoot as follow steps:
1. Make sure the thermostat valve is tightly connected to the radiator.
2. Make sure you are using non-rechargeable 1.5V AA batteries and they are not in low battery level.
3. If you installed with a valve adapter, make sure you use the stick component came along with the package shown in user manual.
4..Factory reset the smart thermostat valve by pressing down the up and down, or + and -, buttons for 5 seconds, and sest up again.