Try a little detective work........
You've had the lens off to replace the bulb, can you remove anymore of the fixture to see if the wires are intact?
It's not difficult to remove the actual plastic switch......I assume it's the kind that's on the underside of the cupboards. Check that the wires are attached at the switch. They may be direct to the light fixture itself. You're only dealing with 12 volts here. Maybe to test and see if the switch is defective, make direct contact of the wires with each other instead of using the switch, and see if that lights the light