Worcester condensing boiler flashing blue light?

hi. I came home to my boiler flashing blue light. I noticed the pressure had dropped right down. I checked furthest away radiator and no air was in it. I then topped up the pressure to 1 and a half and tried resetting. It starts up and makes all the right sounds and blue light is steady for 30 seconds then flashes again. I tried resetting a few times but the same thing happens.