Rear door won't open

The plastic clip on your rear hatch actuator has broken off.
Let me explain in detail. There is an electic actuator inside the lower part of the hatch located almost directly behind the inside pull handle. There are clips that hold two rods to the actuator that go to the locking mechinisms on either side of the hatch. When one of these clips break, one side of the hatch will open, the other will not.
To repair this sort of problem you must first push the outside button to release the lock that is working. Move to the inside of the vehicle. Remove the inside door pull handle located on the hatch. Carefully pull the trim assembly toward you, being careful not to break it. It does have some clips that hold it to the hatch frame so some effort may be needed to dislodge it. Once it is pulled away from the hatch frame, you should be able to look inside with a flashlight and see the loose rod assembly. You will probually need a pair of long needle nosed plyers or a long slim screwdriver to reach the rod. Grab the non working rod with the plyers or screwdriver and pull the rod assembly toward the center of the door. If done correctly you should hear the latch pop open. Push the hatch when you hear it pop. It should now open.
Once open, rempve the rest of the trim assembly to avoid damaging it, remove BOTH rod clips, and go to your local chevy dealer to get new ones. You want to replace both because it will make them easier to match up and the other one is probually about ready to break. Your dealer will probually tell you that they can not get the clip because their computer does not list one but if you ask them to match it up, they can usually find one on their shelf. The clip is about 1-2 dollors, but of course they want to sell you the whole latch 50-60 dollors minimum. If they say they cant get the clips for you try another dealer or a parts store like napa. Good luck, hope this helps, sorry it was so long.