4 wheel drive issues

My suburban has push button 4x4. I just pushed 4x4 high, felt truck engage and proceeded to go. The truck acted as if brakes were depresseed. I stopped put in 2wd and got the same thing. Then put truck in reverse and seemed to unlock it. So i tried again and am getting the same thing in 4wd high, 4wd low, then back to 2wd. Will remain stuck until i go in reverse. Any suggestions!?!?