Spare Wheel Tray Lock Bolt Won't Do Up

[DavidofHook]

In a fit of enthusiasm I undid the spare wheel tray intending to check the tyre pressure on the spare. Bad move. Be warned it requires mucho muscles. Too many for me.
On refixing the tray the removable bolt went back fine and fixed the wheel in position but I could not tighten the lock bolt which is a trapped bolt which hangs down after loosening.
When I screwed it up by hand it jammed, if I put the spanner on it it seemed as if it was cross threading. Being very skilled at cross threading I stopped!
It is now hanging down and is ok as a temporary bodge but i need to screw it back up again.

Any one had any experience on how to sort this?

Many thanks