Your boiler's control panel has detected that one of the buttons on the front display is being held down or is stuck in the pressed position.

DIY fix possible

Switch off the power supply to the boiler at the fused spur or mains switch.Inspect the front control panel buttons to ensure none are visibly depressed or jammed with debris.Gently press and release each button several times to ensure they move freely and 'click' normally.Switch the power back on and see if the error clears.