Did I MIS-DIAGNOSE This Mercedes?? (GL450 no A/C)

Uh oh...
The 2012 Mercedes Benz GL450 is back with a no A/C complaint.
Owner wants it fixed ASAP because he's taking his family to sweaty South Carolina in a few days.
He already replaced the A/C compressor, but obviously that didn't fix the problem.
I perform the diagnosis and make a recommendation.
The owner follows through, but STILL NO A/C!!
Did I make a BAD CALL? Or was the replacement used part DEFECTIVE??
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Enjoy!
Ivan