Could be many things causing the central heating not working – if you have a room thermostat connected, give it a tweak and a tap to make sure it is not stuck.
I misread your original post (green light not on). I think this boiler may have a back up immersion heater for hot water, but relies on the gas for central heating. I am surprised that there is no fault code displayed.
To clarify, can you please confirm whether the gas boiler ignites when you run water from a hot tap?