Your boiler has detected that the water pressure inside your heating system is too high and has shut down to prevent damage.

DIY fix possible

Locate a radiator in your home, preferably one upstairs.Using a radiator bleed key, slightly open the bleed valve to release a small amount of water into a container.Monitor the pressure gauge on the front of your boiler until it drops back into the green zone (typically between 1.0 and 1.5 bar).Close the valve tightly once the pressure is correct.