Electric lift gate does not work. - 2003 Lincoln Navigator

Off the top of my head I would say the control module isn't functioning correctly

Here is how it works !
Liftgate Locking Operation
The lift gate will lock any time the vehicle is shifted out of park on vehicles equipped with an automatic transmission and at vehicle speeds exceeding 5 kph with manual transmission. This happens in conjunction with auto door locks if enabled or independently of auto door locks if the feature is disabled. This ensures that the lift gate is locked anytime the vehicle is shifted out of park or when the vehicle is in motion.
The lift gate lock relay supply and coil sides receive a constant voltage through the battery voltage supply circuit and the ECC fuse. The normally closed contact is connected to ground and the control side is connected to the body control module (BCM). A lock function will occur when a door lock switch activation, keyless entry lock transmission, auto door lock function or a lift gate lock function has been received by the BCM. The BCM will then ground the control side of the lift gate lock relay. This energizes the relay and allows voltage to be applied to the lift gate lock actuator lock control circuit. Since the other side of the lift gate lock actuator is connected to the normally closed contacts of the door unlock relay to ground, the lift gate will lock. When an unlock function occurs the BCM will ground the control side of the unlock relay and the rear doors and lift gate will unlock.
The BCM also runs diagnostics on the lift gate lock relay control circuit and will set DTC B3825 as current and also send a Class 2 message to the DIC. The DIC will display REPLACE LIFTGATE FUSE to inform the driver that a fault has been detected in the lift gate lock circuit and that the lift gate is not locked. Faults that will set the DTC and cause the DIC to display the message could be any of the following:
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An open ECC fuse

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An open or short to ground in the lift gate lock relay battery positive voltage circuit

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A faulty lift gate lock relay

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An open or short to ground in the lift gate lock relay control circuit

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A short to ground in the lift gate lock actuator lock control circuit

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A faulty BCM

Open the liftgate. Remove the liftgate applique. Refer to Liftgate Applique Replacement in Body Rear End. Remove the back up lamp socket (1) from the liftgate applique by turning the socket (1) counterclockwise. Remove the back up lamp bulb from the socket.
Lift gate Applique Replacement
Remove the lift gate trim panel. Refer to Lift gate Trim Panel Replacement .
1
Lift gate Applique Nuts (Qty: 5)
Tip
Disconnect the electrical connector.
Tighten
10 N?·m (89 lb in)
2
Lift gate Applique

Is it the back hatch? Can you pull the rod on the broke side & pull handle at the same time?

take it to any gm dealer...its a recall and its 100 percent free...type in year make n model with recalls after it

FIRST TURN OFF RADIO THEN DISCONNECT NEGATIVE BATTERY. MARK POSITIONS OF WIPER ARM ON THE LIFT GATE GLASS,THEN REMOVE WIPER ARM COVER AND NUT AT THE PUTSIDE OF THE LIFT GATE, THEN THE BEZEL, DONT SCRATCH PAINT ON THE LIFT GATE, REMOVE THE UPPER AND LOWER LIFTGATE INTERIOR TRIM PANELS, DISCONNECT THE ELECTRICAL CONNECTOR AT THE REAR WIPER MOTOR, THEN REMOVE THE TWO BOLTS SUPPORT WIPER MOTOR HOLD WIPER MOTOR IN PLACE WHILE REMOVING MOUNTING BOLTS THEN INSTALL NEW WIPER MOTOR THEN PUT EVERYTHING BACK VISA VERSA.

the actuator is bad for the lock it shares the fuse with the doorlocks if they work and that doesnt you need an actuator very common on the rear hatch

look closely/carefully for recessed screws. Most are usually pop on/ pop off types. Pull/ pry gently.

if they are controled or usually opened electrically, then it is probably a fuse. Check your fuse panel

There is an electric motor inside the lift gate that has failed, it pulls the lock rod down to lock the gate when you press the remote, pull the lift gate trim panel and replace thiws part.