With low water on that boiler the pump should run, as it has only a water flow switch not a water pressure switch, so you should hear a hum
Is the green light 'on' or 'flashing'
Top up the water to 1 bar either way, make sure all your stats are turned up,
after a full summer off, at a guess, the pump is either stuck or a mv in the hotpress is stuck closed (money on the pump)
Everyone should turn their boiler on (gas and oil) every week or so, fo just a few minutes to avoid part seizing up (like pumps) as these tend to be all the callouts for this time of year (mostly pumps)
Always a good idea to schedule your yearly service to this time of year or even better late August where you may still get some summer discounts for servicing