Your boiler is temporarily confused because the reset button was held down for too long or pressed when it wasn't needed.

Reset button pressed by mistake.

What causes this fault?

This fault occurs when the boiler's internal computer registers that the reset button has been held down for more than 15 seconds. It essentially puts the control board into a 'frozen' state because it cannot tell if the button is being intentionally pressed or is manually stuck. To fix this, you usually just need to briefly press the reset button again to clear the memory.