2000 jeep grand cherokee rear liftgate won't unlock, but will lock with switch

first is diagnosis.
you examine and test it. to see if its electrical or mech. failure.
and once discovered that follow that to logical conclusions.

Unlock the doors with the power unlock button then you have to push in on the bottom part of the plastic bezel that surrounds the liftgate handle, while at the same time pulling the liftgate handle outwards. It should open then.

There is a switch, most likely built into the latch, that tells the body control module when the liftgate is open or closed. If that fails what you experience will happen. An open / shorted wire or bad BCM or overhead panel will also cause the "liftgate open" indicator to be on. Try and locate the switch and look for obvious damage.

We had a similar problem with our Grand Cherokee, the actual problem was the latch handle. We ended up taking it to the body shop to get the gate open and the latch handle replaced. I don't remember the actual total but it was under $100 including parts.

sounds like a bad switch in rear hatch, switch is located inside hatch and is bolted to the latch . remove the panel and you may have to remove the latch to get to switch, then replace the switch, also try to un plug switch and see if light gos out, that is a sure way to test it. hope this helps.

lock & unlock the tailgate lock cylinder

You need to remove the panel from the liftgate and unlock and open it manually at the latch. It is not fun, but you can get the panel off with the hatch closed.

there is a button outside on the liftgate where the licence plate light is . push button up to open glass

the electronic sensor could be bad or the lock is physically jammed.