Follow the below steps in order to re-calibrate the TRV to the radiator:

1. Remove the TRV from the radiator
2. Take out one of the batteries, and re-insert
3. The TRV will calibrate and the pin will move open and close (this process takes 5 mins, the pin moves very slowly but you will hear a winding noise)
4. When the pin has recessed back into the valve (not extended), remove the battery (this will lock its position)
5. Screw the TRV back on to the radiator, finger tight (you may insert a 1p coin in between the valve pin and the radiator pin to help with closing the pin)
6. Re-insert the battery and the TRV will calibrate to the radiator