Yes, sometimes they never get better. Last year we found one that couldn't stand. It's mother had it in the central pen in the corral. On her own. It's problem was the back legs. You could stand it up and balance it by holding its tail lightly and it could walk, but the odd thing was, both back legs moved at the same time. If you kept her balanced she'd run all over creation dragging you along behind her. Let go of her tail and in 5-10ft she'd lose balance and fall over, turn her head at you with a look that said "whydya do that for?" Of course I made the horrible mistake of letting my sister get attached to it. So every day multiple times a day I or another person along with my sister would go out feed her and hold it up as it ran around. All the while I was wondering what I was gonna do. I kept picturing the calf a year later still not able to walk and me having to find some way to hold up 700lbs of hoppin and skippin yearling heifer. Luckily I didn't have to make that choice. When I was off working my day job one day, my dad and sister went out to feed it and found the mama standing over it fighting off the buzzards. Since it had to lay on it's side all the time I figure bloat may have got it. When I got home, they had already buried it.
Anyhow, work with it give it shots it might need and a little time. Everything deserves a fighting chance, but set a limit and keep yourself detached. Otherwise, you will end up in a position you don't want to be in... By the way, that was the VERY FIRST calf I ever had. Talk about a great start. That year I went on to have one born dead, another get trampled by another cow in the field and its hip damaged. No one said it would be easy. Good luck, like the others said, try to get it standing. At the least it gets its blood flowing and its muscles and joints moving.