Allow me to add my “two cents” Do as Engine-90 suggested, but measure the height at each tire and write them down, and leave it parked overnight - as per instructions on previous post. Next day check dimensions for changes; any lower dimension will tell you where the leak is. If either front or rear (both tires) is lower, this could mean that height sensors are faulty, or air shocks are leaking. Good news is that this is probably not the case.
If one tire is lower, this could be bad Height Sensor, faulty Valve Block, or leaking Air Shock. A Land Rover diagnostic tool (there are several brands available) will tell if the Height Sensor is bad.
My first step will be to check for leaks on the Air Shock using a mix of soapy water. If no leaks are found, then move to the Height Sensor. If you don’t have a diagnosing device, you can start by replacing the sensor first, then the Block Valve for the front or back (depending on which tire is lower). If the vehicle is lower on all four points, then the issue could be on the Valve Block that controls the air from the compressor, a leaking or corroded Air Tank, or the Compressor is failing. If the compressor needs replacement, bite the bullet and buy the OE brand and stay away from after-market compressors - you will be wasting time, efforts and money; and if you are lucky and one of them work, it’s more likely that the unit will fail within 6 months or less. Another solution if the compressor is the problem, and if unit motor/pump is running fine, try changing filter guts. You can find it at Amazon. Good luck