Your boiler has detected that a button on the control panel has been held down for too long, which usually means a button is stuck or the panel is faulty.

DIY fix possible

Check all buttons on the front control panel to see if any are physically stuck in the 'in' position.Gently press and release each button several times to ensure they click and spring back out.Clean the control panel with a dry microfiber cloth to remove any sticky residue or grit hindering the buttons.Reset the boiler by turning the power off and back on at the fused spur switch.