OBD Non Communication

Went for Wisconsin emissions today with my 2005 Chevrolet Avalanche. The inspection sights main OBD computer gave a Non-Communication code. Tried 3 different lanes at the sight, and still no communication with my Chevrolet Avalanche Went home and plugged in my Actron OBDII tester. Worked great, PASS, No codes found! Went to Autozone and them put thier scanner on, Passed, No codes found. Went back to testing sight, they were having problems with thier mainframe computer. They reset thier system, and still no communication with my Chevrolet Avalanche The manager said it was due to me having an "aftermarket electronic item" installed, an electric trailer brake for my travel trailer. I think not. My truck runs great, no codes, no misfires, no blue smoke. What a joke. Anyone have any ideas?
Gus...