Your boiler is unable to heat your hot water because one of the internal temperature sensors has developed an electrical fault.

No DHW heating - Cylinder temperature sensor/comfort sensor/loading sensor shorted out

What causes this fault?

This fault occurs when the internal electrical sensors responsible for monitoring your hot water temperature stop sending a valid signal to the boiler’s control board. The most common reason is that the sensor's internal wiring has short-circuited or the electrical connections have corroded over time, preventing the boiler from knowing how hot your water is. Because the system can no longer safely regulate the temperature, it disables the hot water function as a protective measure.