Does that lock work using other methods like the button on the door, or keypad/keyfob?
If not, it's likely the door lock actuator mechanism is failing.
See "Related Questions" below for more
Yes , keyless remote entry
Not with the keyless entry pad or remotes - unlock your drivers door using your key That's what I had to do on my 1995 Ford Explorer when the battery had a dead cell and there was no power
If there is a touch pad on the drivers door then it has keyless entry.
One reason that your keyless entry may not work is that the battery is dead, take it an auto parts store and have the keyless entry battery replaced. If that does not fix it you will need to take it to the dealer to have the keyless entry reprogrammed.
asking to the experts
You can unlock all the doors , liftgate and glass using the keyless entry keypad , but to actually get the rear glass to open you have to turn the handle on the liftgate Enter your personal code or the factory code to unlock the drivers door and then push the 3/4 button within 5 seconds to unlock the other doors and liftgate
No
On the inside of the keyless entry remote or sometimes on the back it explains how to do this. I believe you hold the unlock button along with the lock button for 7 seconds near the car. It will explain it on the inside of the keyless entry remote.
Each vehicle has its own keyless entry factory code
No , just to lock or unlock the doors
Each vehicle with keyless entry has its own code
This may sound too obvious but if you have the key, unlock it with the key. If not hire a locksmith.