I just picked up a 2015 rental Tahoe this afternoon that I'll have for a few weeks and the rear hatch won't open. I double press the remote for the rear glass only and that works fine but when I do the same for the whole liftgate, nothing happens except for the vehicle lights flash. Am I missing something here or is it broken? I've already been back to the rental place once to give hem back their piece of crap Jeep Compass they gave me first so I'd rather not have to go back again. Thanks!