how can i fix my sabre he boiler to give heating and hot water?

my was working alright until i turn it off to fix a tap in the bath room.the boiler went red after some days and i reset it by turning it off for some seconds and it worked.but later it stopped given out both water and central heating but the green light keep on flashing and you can hear the noise of normal boiler working but still the water and heating are not working.what is the problem and how can i solve it