on the inside, at the base of the hatch, there is a small doorway that can be opened. once you open it, there is a small white tap that is the linkage to the mechanism. you pull/push on it, and it will open the hatch. After that, im guessing you'll need to have somene look at the electrical relay that opens the door from the pressure pad at the rear.
its at the 4 minute mark
Toyota 4Runner Tailgate Lock Repair Update - YouTube