Your boiler has paused itself because the water pressure in the system is falling outside of the safe operating range, but it should restart automatically once the pressure is corrected.

DIY fix possible

Check the pressure gauge on the front of the boiler; it should ideally be between 1 and 1.5 bar.If the pressure is too low, use the filling loop to top up the system until the needle reaches the 1.5 bar mark.If the pressure is too high, bleed a small amount of water from a radiator to drop the pressure.Wait for the boiler to detect the correct pressure and clear the code automatically.