I assume you got the switch second hand. Did you inquire if you were to purchase a new switch thru GM, that it would include a BCM activation code?
I asked the Tech I am working with to ask that to the Tech line. They have been very helpful in trying to find me a solution to this odd problem. They are surprised they won't do it either.
2016 Colorado LT Diesel
Red Rock, Sports bar, Black 5" assist steps, EGT and Boost Gauge with custom bezel mount
AFE Magnum Intake and Bladerunner Hot/Cold side Kit
Duramaxtune DSP-4 Tuning
AFE Rebel side exit turbo back w/ Black tips