Use degreaser and hot water to remove all the old, hard grease. If it doesn't free up you need to replace it, it's either broken or bent from prying. If it does free up you need to re-lubricate and be aware it may malfunction again.
Full service junkyards often don't like selling latches, collision repair shops like buying panels with that stuff intact. Try a self service yard. Or somebody parting out on craigslist. Good luck