Your boiler has detected a problem with how gas is flowing into the system, which means it cannot light safely and has shut down as a precaution.

Gas valve fault

What causes this fault?

This fault occurs when the boiler's internal computer detects an electrical or mechanical failure in the component that controls the fuel flow. The most common reason is that the gas valve has stopped responding to signals or the main circuit board is unable to communicate with it, often due to age or electrical wear. Because the boiler cannot accurately regulate the gas supply, it locks itself out to ensure your home remains safe.