I took the car, which I bought in 1990, out of winter storage a couple of weeks ago. I noticed that the car was in high mode and didn't hear the usual sigh when the air pressure releases after the key is turned off.

The air suspension switch is on in the trunk,

Then one day the car was very low and the ride quite bumpy as if all air suspension is gone. Changing between high/low does not work.
so my question is what are common faults that inactivates air suspension? Fuse, pump, leakage?

The car is low all around so it is not a single air suspension that falters.