Your boiler has encountered a general electrical failure, likely caused by moisture or damage to the internal brain of the unit.

Other faults not covered by above - Light indication during fault not covered by above details. Control board is likely to be wet or damaged or malfunctioning.

What causes this fault?

This fault occurs when the boiler's internal computer experiences a critical communication failure or hardware malfunction. The most common reason is moisture ingress from a small leak or heavy condensation getting onto the electrical circuits, though the components can also simply fail over time due to heat stress.