Get someone who has the GAP tool (just maybe if unlicensed to your VIN ) it will help.
I have just gone through a similar experience with the level sensors on my L320 and with WITHOUT using MY Gap tool Igot into quite a mess as forgot to disable the suspension unit/module to repair the sensor . It lost communication with the system and guided height calculations would not succeed. I was advised of a hard reset of the battery.
I went into service /test mode and checked the ecu was there and REenabled to Suspension and in Build Mode , ACTIVATE STANDARD.
My own problem remains , I think is , that the Britpart Level sensor is not compatible with the rest of the corners. It sits a little lower than it should.