I had a leak in a pipe to a downstairs radiaotr, drained the system, plugged the leak, refilled system which worked for a few hours then stopped. Now boiler won't come on.

It's the old traditional boiler type with tank in loft not a fancy combi. I can't see a pressure gauge at all as thought maybe the pressure was too low and the pumps themselves seem to be pumping. There are two big red valves next to hot water cylinder which I turned when trying to stop the water off and to be honest have no idea what they do and whether I've inadvertently done something by turning these as not sure whether they were open or closed to begin with.

Help!

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I see 4 valves, 2 with handles and 2 without plus a circulating pump. What are the 2 valves without handles connected to. Are the valves with handles open? You may have an air block, did you bleed the system?