I just reread the post, and it's vague as to what he means. I took it as the fork is stripped and can't be tightened, but it could also be I can't get it started which is a horse of a different color.

If the thread is basically but he can't get it started, probably because dropped the fork and dinged the first thread, or cross threaded it a turn or two by starting badly, then there's something to work with, and all he needs to do is dress out the local damaged area, so the cup will install. He just has to be careful to remove only as much material as necessary so there's still enough to hold on the cup and locknut.

This is the kind of thing that any of us could look at and assess in 5 seconds flat, but it's hard to advise sight unseen. IF the OP is in above his head he should seek the opinion of someone and proceed accordingly. If here's a co-op or local fixit guy that's his best bet, a least for a consult.