[the roadie]

Check fuses 3 and 19 under the rear seat. They run the liftgate control module.

Does your rear window wiper operate?

Do your other doors unlock with the remote keyfob? That would indicate the rear liftgate module is OK, and your latch problems are simple corrosion/rust on the latch mechanism. Remove the liftgate inside panels and look.

If it's not the fuses, or massive water infestation from a bad rear washer hose coming undone inside the liftgate, it's very often broken wires inside the insulation where the harness hinges at the top of the liftgate. Constant flexing is not good for the copper.

 

[the roadie]

Check to see if the rear wiper are working at the same time....

Uh, did you see my post #4? :hopeless :tiphat

 

[the roadie]

If the wiper works, then the liftgate control module has power, and you certainly have a mechanical corrosion problem with the latch mechanism.