If you open a door,bonnet or tailgate it stops the air suspension self leveling. The car with all doors etc closed will automatically check for level then let air out to remain level. Its a bugger if you have a leak in one bag as the car ends up on its bump stops.
Its more convenient to open the top tail gate to disable this feature while you work on the car.
Just check the plug is connected on. have a look at this thread
https://www.landyzone.co.uk/land-rover/p38-select-neutral-message.42968/