I just took the drive shaft out of my Gen Coupe to put in new flex disc. I don't know if your has such a set up. But the nuts you take off from both ends are reverse threaded. The heads, which face towards the trans or diff, have a concave head which you can feel but cannot see.
Some years ago I change the outer rubber bellows on the drive shafts in our 2006 Getz 1,1. The nuts was not a problem and I do not remember, that the threads was left turned. But of course that would explain your problems. You better check which way to turn the nuts.