In my case, I wasn’t getting an error; rather, it would settle at night.
It ended up being a leaky right front strut. I was trying to do the cheapest fix first! I suspected the prior owner had not serviced or replaced the compressor and hoped it was just dessicant stuck in the valve seat.
You can pull the fuse for EAS and see what happens overnight. I would go full height, pull the fuse. Just make sure you put the fuse in the right slot! I put it in the open slot below and spent a lot of time trying to connect to the ECU with my GAP tool. There was no power to the ECU until I moved the fuse to the correct spot.

 

What about the "Too Many Attempts" code you mentioned in the first post?

I got that one regularly then it sort of stopped. I also did do the leak detection and the front sagged in unison.

 

First time I cleaned mine, there was quite a bit of white powder - fix was good for maybe 6 mo tops
But I made the mistake of cleaning too close to the compressor refresh
I also cleaned the back one

2nd time cleaning the front, I didn't see near as much white powder
but the after is still holding up nicely even when unused for a few days
only have maybe 2 mos on the recent clean - back is still 100% from the one cleaning

I guess my point is, it doesn't seem to take much powder to allow the seal to leak, so don't be discouraged if it doesn't "look bad"

 

Mine just had a light powder to it. There was not much actual material in a way that could be shaken off, etc. Just enough small particles to prevent 100% sealing. I rebuilt my front with new o-rings and have not had an issue yet. I never actually got around to doing my center or rear block yet but all seems well.

 

Would it be expected that the suspension would adjust some if it's not parked on level ground? This morning the compressor ran and the Rover adjusted... but my driveway is not flat. I guess to really know if I fixed anything I should measure again...but just wondering if there is consensus that on a sloped driveway all bets are off....

 

Clarify a little. Ideally you want to measure on a flat surface but it does not need to be level in the sense of putting a picture up on the wall. Its not like the truck can tell if the surface you are on is 20 degrees off. As long as the overall plane it sitting on is flat. Otherwise your measurements will of course be off - just like sticking a brick under just one wheel on what would be a 100% flat surface.

 

I know that when I measure it has to be flat....all I mean in this case is that today it raised up after sitting overnight, and I'm trying to comfort myself by saying "oh that's because the driveway is sloped" rather than the alternative that the new valve block didn't fix anything.

A measurement on a flat surface will have to wait until maybe Wednesday.