DIAGNOSIS You've likely got a burnt-out oven lamp. On these models, the same bulb is used for both the door-switch operation and button operation. If it's dead, neither method will work.
FIX The bulb is in a socket at the top rear of the oven cavity. Make sure the oven is cool and unplug the range. The bulb cover is usually a glass dome held by a wire bracket or a screw-on metal shield. Carefully remove it (it might be hot if recently used). Unscrew the old incandescent bulb (it's a standard 40-watt appliance bulb). Replace it with a new 40-watt appliance bulb. Do not use a higher wattage. Replace the cover, plug in, and test.
IF THAT DIDN'T WORK If a new bulb doesn't light, the problem could be the light socket itself (corroded or broken) or a wiring issue back to the control board. The door switch could also be faulty, but that's less likely since the panel button also fails.
HEADS UP That bulb gets extremely hot. Let the oven cool completely before attempting replacement. And seriously, don't up the wattage—you can melt the socket or create a fire hazard.