First make sure you have gas. Do this by lighting the stove or hot water heater. This sound stupid but you have to know this before going further.
Test it by holding a match at the burner while someone turns it to gas. If it lights and has a good color and shape to the flame you have a igniter. If the flame is poor you have a clogged burner tube, most likely a spider nest. If it does not light at all the control board may be bad. If the flame remains only as long as you have the match in place, and don't remove it for at least 10 seconds, the thermocouple is bad
The spider is the most likely.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles