HOW CAN I FIX MY VOKERA COMBI BOILER?

The amber light then red light comes on several times a day,it stops the heat from automatically coming on when on timer.i had the boiler cleaned and serviced.i was told to turn the filling loop so as to bring the pressure bar back up but this is only a temporary fix.the water then runs out of the pipe outside.creating the same problem all over again.