Your boiler's control panel and its main computer are having trouble communicating with each other, meaning you cannot change settings or see the boiler's status correctly.

Local user interface fault

What causes this fault?

This fault occurs when the data connection between the front display screen and the boiler's internal computer is interrupted or fails. The most common reason is a loose internal wire or a component failure on one of the circuit boards caused by general wear and tear over time. Because the 'brain' of the boiler can no longer talk to the control panel, the unit stops operating for safety.