My driver door latch failed a few months ago.....it would latch, but not lock either with the remote or the key. I sprayed the hell out of it with everything....nothing. The problem seems to be the spray won't penetrate into the part that's actually sticking.
It's possible if you took the thing off the car, it could be partially taken apart enough to lube the inside and free up what's stuck.
Mine got replaced under the basic warranty. $80-$120 if you have to buy one plus labor if you can't do it yourself.