Your boiler’s internal computer boards are having trouble communicating because they haven't been properly synced or configured to recognize each other.

No valid appliance variant for display and/or electronics: Spare part case: Display and electronics changed at the same time appliance variant not re-set

What causes this fault?

This fault occurs when the boiler's internal control boards fail to recognize the specific model they are installed in, often because the 'identity code' has been lost or not set. This usually happens after a physical repair where both the main circuit board and the display screen were replaced simultaneously, leaving the system without a master record of its own configuration. Without this data, the boiler enters a safety mode because it doesn't know its own power rating or technical specifications.