Your boiler has stopped working because it has detected a major internal error that has forced it to shut down for safety reasons.

Appliance lockout and power failure

What causes this fault?

This fault occurs when the boiler's control system detects a complete interruption in electrical supply or a critical communication failure between internal components. It often happens because a fuse has blown on the main circuit board or because the board itself can no longer process power correctly. In some cases, loose wiring or a sudden power surge can trigger this emergency shutdown to protect the appliance from electrical damage.