Your boiler has lost communication with the main thermostat or temperature sensor in your primary living area, meaning it doesn't know when to turn the heating on or off.

DIY fix possible

Check if your room thermostat or sensor has run out of batteries and replace them if necessary.Ensure the thermostat is within range of the boiler and has not been moved behind a large metal object or thick wall.Try restarting the boiler using the Reset button to refresh the sensor connection.