By lifting the car, the shocks extended, so the computer would have tried to deflate them while it was in the air, not inflate them. The car would be sitting too low when it was put back on the ground.
To be sitting too high, I suspect, is not the clue. The problem is it is not adjusting. That suggests a problem with the rear height sensor. I would start by looking at the link between the rear suspension and the body. If that link is broken, disconnected, or rusted apart, the sensor could be telling the computer that the car is at the correct height and no adjustment is needed. Those links typically first cause a problem right after hitting a big pot hole or from raising the car, (even to change a flat tire on the side of the road), because that causes the sensor to travel beyond its normal range. If a problem with that link occurred while the car was on a hoist, there's a real good chance the mechanic didn't do anything to CAUSE the problem. There was a problem just waiting for the right set of circumstances to occur.
Depending on what work was done, it's also possible the mechanic disconnected the link to prevent the system from performing an undesired operation while in the air, and he forgot to reconnect it. Depending on where the sensor is positioned, the system will then either try to constantly lower, or constantly raise the car, or constantly leave the car where it is.
Pump failures are real common too with all of these systems. If the height sensor's link is okay, and the fuses are okay, you'll need a scanner that can access the load-leveling computer to see what the computer sees. If the scanner shows the computer is trying to deflate the shocks, but without success, suspect a shock absorber that is stuck in the full-up position. That will eventually correct itself after drive down enough bumpy roads. That happens more commonly with front struts, but shock absorbers are built essentially the same way, just smaller, so the same thing can happen. Once a stuck strut or shock releases, it won't cause a problem again until maybe the next time the car is raised on a hoist because they don't travel to that fully-extended position during normal driving.