6 years old. Blower runs, ignitor glows, natural gas valve clicks but no flame. Blower remains on ignitor glows & cycles 3 times but never fires. Is it the ignitor (not hot enough) or the control valve? I've got a Simpson meter but don't know what values I'm looking for.I had same problem with a gas stove once.Turned out to be the ignitor, even though it glowed. Any help ? Thanks.

Check this page for some info on testing.

Hot Surface Furnace Igniter Education

A cold ignitor will have a reading of between 20 and 300 OHM's They should also have 110/120 volts to operate.

Honeywell smart valves are a bit different and they work on 24 volts

Luxaire uses a 110VAC igniter. Don't forget to clean your temp sensor. Are you sure the gas valve is opening? There are a number of relays that click on some models. The only way to be sure the valve is actuating is to check the wiring to it.