Sounds like your linkage is bound up.
Crawl under the jeep from the drivers side. Look up next the the transfer case and you'll see the linkage. You'll see this:
To the rear of that bracket the connecting rod runs to it's swivel point. There is a set screw on it and it holds the connecting rod into place.
Get someone to sit in the jeep (off, in gear, parking brake set) and shift/try to shift into 4hi/N/4lo while you watch. You should be able to see if something is bent or binding.
Sometimes, you need to loosen the set screw mentioned above, shift the tcase into 4lo manually (all the way forward), place the connecting rod in place and have your helper put the shifter into the rearward/4lo position and then tighten the set screw.
If it's bent and binding and you can't straighten it or adjust it to work you may need a new one. Pretty simple to do and there are a couple of aftermarket ones in addition to the OE shifter brackets.