I am having the same problem with my porch light too. I was even showing 12+ volts and the light wouldn't light. Finally had wires (both pink) pulled as far as they would go, traced up to the vent and to the front reading lights. Get 12V
but not enough amperage to light a bulb - tough to figure. I can run 12 volts from somewhere else to the switch and the light works. The joint has apparently gone bad somewhere I can't reach it. I tried threading a new wire in, and just couldn't get anything to quite connect where I could get a wire hooked to it to pull. I finally put it all back together for now. May have to surface mount a new wire on the inside wall and put one of those wire covers on it unless I can figure out how to get another source of power there. Otherwise have to pull the interior skin, don't want to do that!
Otherwise may just put one of those LED self powered units there for now. I really miss the porch light!
I would suggest you run a good source of 12v
to the switch and see if that doesn't make your light work, just to see if it is a corroded high resistance connection.
By the way, take those switches which stop working and soak them in alcohol or similar overnight, it usually cleans them out and they are good as new.