Your boiler is struggling to talk to the gas valve, which means it cannot safely light the flame to provide heating or hot water.

Gas–valve control – defective; Short circuit/earth (ground) leak in cable loom to gas valves, gas valve assembly defective (earth/ground leak from coils), electronic control system defective

What causes this fault?

This fault occurs when the boiler's main computer loses the ability to send signals to the gas valve, which is the component responsible for letting fuel into the burner. The most common reason is an internal electronic failure within the gas valve itself or a fault on the main circuit board that prevents it from controlling the combustion process safely.