4.8is Self Leveling Inactive error

[dlh1228]

After towing a heavy trailer this weekend, I now have the dreaded Self Leveling Inactive error. My suspension was not sitting low at all. All 4 corners look good. I checked the two fuses in the rear trunk for the air suspension and the fuse in the glove box and all fuses were good. I then removed both rear tires and checked to make sure the joints on the ride height sensors were not stuck and I cleaned and greased the joints. I replaced the airbags with new Arnotts about 2 months ago, so The bags are new. I de-pressurized the system by letting some air out. With the key turned on and engine running, my compressor is not turning on to raise the rear back up. The ride height switch on the dash has the green light on in the middle position. OBD2 code reader showed no codes. Any help would be greatly appreciated.