Your boiler has detected a flame when there shouldn't be one, which usually means a internal component is stuck or damaged.

Permanent ignition

What causes this fault?

This fault occurs when the boiler's sensors detect a flame still burning even after the heating or hot water has been turned off. The most common reason is an internal component like the gas valve becoming stuck open or an electrical failure on the main control board that keeps the ignition system active. Because this involves gas flow that isn't being controlled properly, the boiler shuts down immediately as a safety precaution.