Your boiler has lost its flame while running and cannot manage to restart itself, likely due to a temporary interruption in the gas supply or a component failure.

Flame goes off during operation and subsequent ignition attempts failed: Gas supply temporarily stopped, ignition transformer has spark failure, faulty earthing of appliance

What causes this fault?

This fault occurs when the boiler’s flame is lost while it is already running, rather than failing to start initially. It is usually caused by a temporary drop in gas pressure, a build-up of debris on the ignition components, or an electrical fault that prevents the boiler from detecting its own flame. When the system can no longer confirm a stable flame is present, it shuts down as a safety precaution.