more info would help............but if it is only 4 yrs old it will not have a pilot light, it will be auto sequential ignition.
If it gets to the ignition stage and starts to spark at the burner, most of the sequence has been checked be the pcb.
If there is no ignition at all of the burner before lock out then no gas is present. Check the simple things first............has the supply been accidently turned off.
You would be suprised how often this is the cause.
Gary C.
December 2008