Truss Rod problems, need help.

Hello.
I'm currently fixing a guitar. It seems to be an imitation of a Gibson Les Paul. It's written Riviera on the Headstock and that's it.
( It's not an Epiphone Riviera )
The only thing left to do is fix the neck. The string are very close to the frets, the last frets are touching the strings. I've tried loosening the nut on the truss rod. Tightening the bolt on the the truss rod with an Allen Key does nothing but when I loosened it, the bolt just came off. Nothing is changing on my neck's bow. I can put the bolt back on but if I try adjusting it again, the bolt comes off or it just doesn't tighten.

What should I do, is this normal or do I need a new truss rod and bolt?

Thanks.
:)