2004 Jauguar XJ8 20,000 miles

Check for a air ride power switch in the trunk. It may be turned off due to a leak or bag problem

You need to see it the compressor is working when the car is running, the air suspension resivoir is in the trunk, itmay have been damaged. Use some kind of soapy water to check for leaks. The car has no switch to turn off the air suspension. It has amodule that will raise and lower suspension even after the car is off.
If you lift the car. Make sure you lift evenly or with the key off. This will make suspension module confused. Disconect battery for 5 minutes and retry