Your boiler's internal computer parts are failing to talk to each other, meaning the system cannot operate or provide heat and hot water.

No Connection To Primary PCB

What causes this fault?

This fault occurs when the boiler's main control board loses its communication link with the other internal electronic components. The most common reason is a failure of the printed circuit board itself, though it can also be triggered by a loose wiring connection or a faulty user interface display. Because these parts cannot 'talk' to each other, the boiler shuts down as a safety precaution.