worchester 24i junior problem

[djcplumbing]

can anyone tell me why it is not firing up, you go to turn it on, the pump is running then you can here it try to ignite (clicking) then it goes of and the red light keeps flashing?

 

[wnjswozo]

check high limit stat ,has,nt tripped (check on top of boiler),then check the basics ie gas supply,boiler pressure