Replaced transmission will not Move

Hi, I just recently replaced my vehicle's transmission with a GMC Envoy 4l60e transmission same all the way around. The problem I am having is that it is not going into gear. We had it in neutral once and rolled it back and when I hit the gas when I shifted to drive it stopped. We also lifted the rear tires and it made a little nudge that was it. You can hear it switching gears as it revs when you do so, even checked the linkage and switched out the pnp switch with no luck. I am at a stand still.