Your boiler is trying to start up, but it cannot detect a successful flame to get the heating or hot water going.

Failure during start-up: Ignition unsuccessful — Gas meter defective or gas pressure switch has triggered, air in gas, gas flow pressure too low, thermal cut-out has triggered, condensate route blocked, incorrect gas injector, incorrect spare gas valve assembly, fault on the gas valve assembly, multiple plug on PCB incorrectly plugged in, break in cable harness, ignition system (ignition transformer, ignition cable, ignition plug, ignition electrode) defective, ionisation flow interrupted (cable, electrode), incorrect earthing of product, electronics defective