Your boiler is unable to release gas into the burner because the internal electronic valve is not operating correctly, meaning it cannot ignite to provide heat or hot water.

Fault: Fuel valve not working - Gas valve assembly stepper motor defective or not connected

What causes this fault?

This fault occurs when the boiler's main control board tries to open the gas valve to start the heating process, but it receives no response from the valve's motor. The most common reason is that the internal electronic components of the gas valve have failed, or the wiring connecting it to the computer has become loose or damaged.