Your boiler has disabled your heating system because it cannot detect or communicate with the controls that request heat for your radiators.

All Heating Zones locked

What causes this fault?

This fault occurs when the boiler’s main computer loses touch with your heating controls or receives conflicting information about how many heating zones it should be managing. It is essentially a 'handshake' failure where the boiler disables the heating to prevent damage because it no longer knows which part of the house is calling for heat. The most common reasons are a loose connection in the wiring, a failed external thermostat, or a software glitch on the main circuit board.