Your boiler's control panel and its internal computer are having trouble communicating with each other, preventing the unit from starting.

User interface fault

What causes this fault?

This fault occurs when the display panel on the front of the boiler loses its digital connection with the main internal circuit board. The most common reason is that the wiring between these two components has become loose or damaged, or one of the boards has suffered an internal electrical failure. Without this communication link, the boiler cannot receive commands to turn on and must shut down for safety.