Are you talking about the rear doors (p/s and d/s) or the lift gate?
If it's the lift gate, you most likely have corrosion, a build up of gunk or lack of lubrication in the release mechanism. Try drowning it in wd40 or similar and see what happens. There is adjustment for the latch too. You simply loosen the screws holding the mechanism to the lift gate and move it into a better position and then retighten the screws.
while pulling up on the latch, try banging your license plate,
tends to get it unstuck... LOL
p.s. that technique is trademarked by SteezeMcqueen
I have to squeeze the handle and push the tailgate in to get mine to open most times. Annoying, but it always works.
again, i've been having the same problems. it seems like the latch mechanism was causing all the troubles. i replaced it today with a new one and now ALL of the moving parts in the tailgate, including the outside handle, are working smoothly. when i pulled out the old latch assembly it was corroded and full of dust and the lube had long since dried out. email me at [email protected] if you want instructions and photos on how to take apart the tailgate. it's pretty easy.