I have a 1999 Suburban that has several of the door latches that do not operate properly with the remote button or the power door lock button on the door. If your locks open okay with the key, it is most likely the lock actuator that is the problem. The coils on these can get weak and not be able to operate the locking mechanism. Changing them out is probably required. Haven't actually changed mine yet, but have taken door panel off to lubricate actuator rod. This helped only briefly. Good luck. The actuators themselves are quite expensive from the dealer. ($60-$80 each, excluding installation)
If you mean the door handle on the inside of the vehicle, it is probably broken. So, when you pull on it it can't pull the actuator rod. You have to change the handle assembly. They cost about $40. (Got one on Ebay for $17+change, we'll see how it goes) But you have to drill out the rivet. So buy a pop rivet gun (good tool to have but you can use a screw and nut and Loctite in lieu of a rivet) and a trim removal tool. The trim removal tool is really important... you CANNOT remove the inner panel the old fashioned (big screwdriver) way. Don't even try. And yes, YOU MUST REMOVE THE INNER PANEL. It has a plastic stem that inserts into the latch assembly so you can't move the latch assembly until the panel is off. 1. Un-bolt the window regulator panel (after you have removed the trim panel) -- I see no need to remove the window regulator panel - You did need to py the switch panel up and off the door (and pull the slide in keepers on the plugs so you can then pull the plugs -- 2. Pull the top the panel back a bit. Lowering the window about 3 inches will help. But, don't pull on the panel too hard. 3. Stick rim removal tool in there and pop off the power door look rod. 4. Use your hand and pop off the handle actuation rod 5. If the bustred part is on the actuator rod and you don't have the replacement yet... leave it in place and tie a rope to the rod and broken piece. Now your lady can get out of the beastie without crawling through the window... . Drill out the rivet on the latch assembly 6. Slide assembly forward and remove. 7. Do things in reverse to reassemble.
If it is the door lock actuators that don't work all the time it is the rivits that hold the actuator in place. They elongate after many uses and the travel of the actuator is not enough to always over come the now longer distance to lock or unlock the door. If you can still hear the clunk of the actuator when you press the door lock it is still working. After taking off door panel. Drill out the rivits and replace with short screws. Short so they do not interfere with other things moving inside the door.