how do i get my pilot light back on my glow worm space saver 50 mk2?

my pilot light has gone out, ive turned off electric point, turned gas knob to off, ive followed instructions on sticker on boiler! push in knob A and hold then push ignite clicker button pilot light comes on, i hold for 20 secs then release knob A. Then pilot light goes out! im doing what is advised but no joy!!!!! can anyone help me please!!!!! I have two little girls and need the boiler to work asap!!! PLEASE HELP.