Your boiler has detected that one of the buttons on its control panel is permanently pressed down, preventing it from functioning correctly.

DIY fix possible

Switch off the power supply to the boiler at the fuse spur for 60 seconds.Inspect the control panel buttons to see if any are physically jammed or stuck down.Gently press each button several times to ensure they are free-moving and not trapped by dirt or housing debris.Switch the power back on to see if the error clears.