2000 blazer 4wd trouble

I go to try my 4wd,prees button to go to 4HI and it seems like it wants to go but goes back to 2HI.I stop car and try it,it goes into 4HI but when i try to go
it wont move,like its locked or stuck,but it seems like its engaged.
I rarely use the 4wd so any ideas?

See the How to/Tech section on this.

Try reseting it. This has been gone over many posts. If not in FAQ use search.