Your boiler has stopped heating because the external temperature control device, typically a thermostat wired to the flooring heat system, is not communicating with or is disconnected from the boiler.

DIY fix possible

Check if your room thermostat or underfloor heating controller has power or dead batteries.Ensure the external thermostat is set to a demand temperature higher than the current room temperature.Check that any electrical switches or isolation spurs associated with your heating system have not been turned off.