Your boiler has lost its connection with the thermostat or room controller, meaning it does not know when to turn the heating on or off.

DIY fix possible

Check if the batteries in your remote thermostat need replacingSwitch off the electricity supply to your boiler for 60 seconds and turn it back on to reset the connectionEnsure your wireless receiver is plugged in and that no large metal objects or new electronic devices are interfering with the signal