Re: faulty tailgate window xy wagon
A number of things to check. I am assuming that neither the interior switch or the key switch in the tailgate works. Appears power is not getting to the motor. There should be a 30 Amp circuit breaker supplying power to both switches - check for 12V both sides.
If this is OK, unscrew the cover plate for the tail gate from inside the car. Then check for voltage getting to the tailgate winder motor whilst some one operates the switch. If there is voltage, motor or limit switch inside tailgate could be stuffed. No voltage - have to find the break in the line.
To get the window down, the regulator arms should be able to be removed with the cover off the tailgate, and the glass lowered by hand.