I have a sabre he boiler that fires up initially then cuts out to red light?

I have a problem with a sabre he 35 boiler the problem is I have reset the boiler re pressurised and done all the usual things for start up I came in to the restaurant to find the water pressure had reached 3 on the gauge so drained it back to just over 1 the boiler fires up initially then before full ignition it cuts out and has a solid red light it doesn't give either hot water or central heating not sure what else I can do