Your boiler is having trouble communicating with its control panel, which means it isn't receiving the instructions it needs to provide heating or hot water.

User interface connection fault. Check wiring between mainboard and user interface

What causes this fault?

This fault occurs when the data link between the boiler's internal computer and the front display panel is broken, preventing the two parts from 'talking' to each other. It is usually caused by a loose plug, a damaged wire, or a failing electronic chip on one of the circuit boards. Because the boiler cannot confirm its settings or safety parameters, it stops running as a precaution.