Right, progress I think. The first scan showed up these codes:
5 Faults Found:

00775 - Level Control System Sensor; Rear Right (G77)
008 - Implausible Signal - Intermittent - MIL ON
Freeze Frame:
Fault Status: 10101000
Fault Priority: 3
Fault Frequency: 1
Reset counter: 188
Mileage: 253030 km
Time Indication: 0
Date: 2022.03.18
Time: 08:15:27

01768 - Sensor for Vehicle Leveling; Right; Supply Voltage
002 - Lower Limit Exceeded - MIL ON
Freeze Frame:
Fault Status: 11100010
Fault Priority: 3
Fault Frequency: 4
Reset counter: 190
Mileage: 253030 km
Time Indication: 0
Date: 2022.03.18
Time: 08:15:44

02646 - Plausibility of Level Control System
008 - Implausible Signal - Intermittent
Freeze Frame:
Fault Status: 00101000
Fault Priority: 2
Fault Frequency: 1
Reset counter: 230
Mileage: 253032 km
Time Indication: 0
Date: 2022.03.18
Time: 14:46:59

01397 - Venting Solenoid for Level Control (N111)
011 - Open Circuit - Intermittent
Freeze Frame:
Fault Status: 00101011
Fault Priority: 2
Fault Frequency: 1
Reset counter: 230
Mileage: 253039 km
Time Indication: 0
Date: 2022.03.18
Time: 17:53:59

01399 - Relay for Level-Control Compressor (J403)
011 - Open Circuit - Intermittent
Freeze Frame:
Fault Status: 00101011
Fault Priority: 2
Fault Frequency: 3
Reset counter: 230
Time Indication: 0

After clearing all these, the compressor jumped into life and the car started to lift. Height settings now on again instead of greyed out and the car stays up. The yellow warning light is still on, however, and a new scan brings up this fault:

1 Fault Found:

01768 - Sensor for Vehicle Leveling; Right; Supply Voltage
002 - Lower Limit Exceeded - MIL ON
Freeze Frame:
Fault Status: 11100010
Fault Priority: 3
Fault Frequency: 1
Reset counter: 190
Mileage: 253039 km
Time Indication: 0
Date: 2022.03.25
Time: 18:24:45

So, do you think that could have been the problem all along? And hopefully a simple fix of changing that sensor? If I can find where it is, that is! Any thoughts? It seems strange that the whole car dropped suddenly at al corners when there were no perceivable leaks from anywhere before that point.