baxi 105he wont relight?

HI MY GAS WAS TURNED OFF TODAY FOR 10 MINS NOW I CANT GET MY BOILER TO RELIGHT IT JUST SHOWS THE flame failure i have cracked open the gas pipe at the boiler to perge the the pipe i have gas to the boiler but it still wont light the fan dose not start up and i just get lockout on the rest any help plz ps all was spot on untill gas supply was interrupted