A friend told me that it is necessary to reset a solenoid valve after changing the gear oil.Does anyone know what it is and how to reset it? Thanks

Looking at the manual gear box there does not appear to be anything to reset just replace oil, check level and go
Connect the Land Rover approved diagnostic equipment. Start and
run the engine.

After filling automatic gear box

1. Using the diagnostic equipment to monitor the transmission fluid
temperature, allow the temperature to reach 60 degrees C.

2. Move the selector lever from 'P' through all the gear positions,
pausing in each gear position for 2-3 seconds and return to the 'P'
position.

3. Raise the vehicle.

4. WARNING: Wear protective gloves.

• NOTE: The fluid level plug and drain plug both use
the same point on the transmission. The inner plug is
the level indication and the outer plug is to drain the
fluid.
Remove the transmission fluid level plug.

5. With the engine running a small amount of fluid should drip out of
the level plug.

6. CAUTION: A new O-ring seal is to be installed.
Install the transmission fluid level plug.
Torque: 7 Nm

7. Install the front undershield.
Refer to: Engine Undershield (501-02 Front End Body Panels,
Removal and Installation).