Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit, usually due to a fault in a sensor or its wiring.

No DHW heating: Cylinder temperature sensor 2 lead break

What causes this fault?

This fault occurs when the boiler's control board loses communication with the sensor that monitors the heat of the water leaving the unit. It is usually caused by a physical break in the internal wiring or the sensor itself failing due to wear and tear. Because the boiler cannot safely confirm the water temperature, it shuts down to prevent the system from overheating.