Gas won't kick on

My kenmore dryer turns on, drum spins but the gas does not kick on. Is this a sensor that could be bad? If so, is there a way to test the sensor? If it is not the sensor - what else could it be?
Thanks

Does the ignitor turn on?

I cant tell. it looks like you have to take the dryer apart just to get to the ignitor and burner assembly.

On my kenmore gas dryer there is a little view hole on the bottom left side of the front panel (might be covered by a plastic plug).

ill try that. thanks