If the ignitor is not getting red, the thermostat, oven safety valve, or the ignitor coulc be bad. You need to test the voltage between the yellow and white wires at the ignitor with the oven turned on. If you read voltage, the ignitor is bad.
If you don't read any voltage, test between the yellow wire on the ignitor and the white wire on the oven safety valve that comes from the range wiring. If you have voltage, the gas valve is bad. If you don't have any voltage, the thermostat is bad.
I hope this helps. If you are not comfortable testing voltages, you can go to [services.sears.com/shs/category/repair?sid=MMLxexpertxmerch
] and get a Sears technician to repair the range.