Tailgate actuator on 2005 envoy xuv won't unlock

Latch actuator is probably bad an needs replacing . Your best bet , take it to a qualified repair shop. An have it checked .

Take your vehicle to a qualified repair shop ! You have not the knowledge or testing tools to even begin to diagnose this .

check the fuse/relay. if it is neither of these check the switch with a multimeter. If you can hear the motor trying to move the glass when you try the switch it may be the regulator needs attention. It may be the motor needs to be replaced.

check fuse and relay along with the switch first then the regulator and motor afterwards. Replacing the small electronics is obviously easier than having to open up the tailgate to check the mechanics of the winedow.

The tailgate assembly requires regular lubrication and adjustment in order to keep functioning properly. If it has stopped functioning, follow the manufacturer's recommendations for periodic lubrication and adjustment.

Dealer or a junk yard

this is the exploded view of tailgate https://www.gmpartscenter.net/v-2004-gmc-envoy-xuv--sle--4-2l-l6-gas/body--tailgate this is removal and working on an xuv https://www.youtube.com/watch?v=MLQLAD8xOPk

do you have the tailgate with the window in the upper half and does the window open?

1) Look for fuse 32 in underhood fuse panel, I believe this is for trailer lights. 50 & 51 are for R and L trailer brake.
2) The blower resistor pack is defective, this is located behind the glovebox and mounted to the blower body.
3) I have no solution for tailgate problem, suggest visiting Trailvoy.com forum and doing search on XUV tailgate.

pull the plastic off of the tailgate and make sure the small wire looking controls are still hooked up. sometimes they will pop out after alot of use. other thing is make sure the rear actuator is actually working (it could be bad)

the actuators have a white stem that sticks out of the bottom of them. if you push up on the ones on the driver side it will open the back hatch for you.