Neither the key fob or unlock button on d/s door will unlock the lift gate (2003), what should be looked at?

When the gate was used manually the inside button was deactivated. Look in owners manual or contact dealer to see how to activate switch.

Sarah, I believe you have to use key or key fob. to open/unlock lift gate.

rear door hatch lock repair GMC Chevrolet - YouTube

? 4:26
https://www.youtube.com/watch?v=QS3PMhGgyAg
Apr 5, 2014 - Uploaded by auto resource
2002 Yukon, rear hatch lock not locking. ... rear door hatch lock repair GMC Chevrolet. auto resource ... chevy tahoe lift gate notopening - Duration: 2:12. ... A Method how to unlock your car in 10 seconds :) - Duration: 0:35.

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? 2:12
https://www.youtube.com/watch?v=xU6ybiY3F4I
Sep 1, 2010 - Uploaded by 76bluemoon
Back lift gate/glass would not open or release. Even when unlocked with the key fob or the unlock switch on the drivers/passenger door. ... How To Install Replace Rear Lift Gate handle 2002-09 GMC Envoy Chevy Trailblazer ...

please explain the language here as iam at a loss -LIFT GATE??? do you mean the back door or tailgate ,sorry its getting late in this time zone and i think its near my bedtime

Before you go running down the rabbit hole, i.e. reprogramming key fobs, replacing the Lift Gate Module, removing body panels looking for broken wires; do two things:
1.) Open every door and slam it shut.
2.) Almost every auto parts store has a key fob test station, verify the key fob is transmitting.
Those two simple steps will solve it most of the time. If not... I hope you like carrots.

Check it out on you tube !

do you have a second fob try it battery may be low may need reprogramed or replaced check with your dealer

Your door lock actuator have issues

I just want to know if there is any manual to disarm the lift gate and check for the problem. Currently my door is lock and cant open, how you force it to open?