Your boiler has stopped providing hot water because the internal sensor that monitors water temperature has developed an electrical fault.

What causes this fault?

This fault occurs when the electrical connection within the hot water temperature sensor fails or is damaged, often due to internal wear or moisture ingress. When this happens, the boiler's control board can no longer read the water temperature accurately and shuts down the burner as a safety precaution. The most common cause is a failed internal component within the sensor itself or a wire that has become trapped or frayed.