Working solution for 01 S430 Airmatic Issue, Nothing has worked

Car is a 2001 S430. I am mechanically inclined but not familiar with this vehicle.
I have been battling a airmatic issue for a while now. First off, car was sitting low. airmatic service indicator. So we take it to a shop. compressor replaced, drive it for a while and still sits low, not pumping up. I check relay, its fine. Take it to a Mercedes dealer, they tell us it needs a new control computer and they want $5000 to do it, not gonna happen. So I order and replace the control computer and nothing. Car is sitting dangerously low, indicator lights on, pump will not run.

What is there left to do/check?

Working solution/advice:
My advice would be to become as familiar as you can with the Airmatic system by reading all the posts on this forum as well as Benzworld. Try finding the problem with that knowledge.

What has helped me the most with the repairs on my ’01 S430 is having a copy of the MB WIS program, (Workshop Information System) which is used by the techs at the dealerships? You can purchase a copy on eBay on DVD’s relatively inexpensively. Armed with the actual work instructions used by the dealerships you can repair any system on your car.

There is no one size fits all for fixing the Airmatic system but if you are methodical and patient you can do it.

One last thing to suggest, if you are still stumped, you can find an independent (Indy) shop with an SDS (MB Star Diagnostic System) and have them do a diagnostic which should tell you the exact component that has failed.