Friend of mine has "Air Suspension Inactive" on 2002 L322 dash. Car is at std height and drives ok. The button inside rotary switch is lit up. If you turn rotary switch to adjust height the desired height light flashes but nothing happens and std light comes back on.

Try resetting it, this is done by turning steering wheel fully left and then fully right (or the other way round I forget). It will go' inactive' if you have had flat battery etc.

PS It is much easier for yourself if you use the search function in the right hand corner of screen as this has undoubtably been covered before and you'll have your answer straight away.

..................Adam