No Crank, is this a computer issue that needs to reboot?

Was the battery disconnected before the mechanic started the repair? It should have been. Sounds like a BCM problem. Lights, accessories and possibly the security system are controlled by the BCM. Are all the ground straps hooked up? Everything clean and tight? Has the starter been bench tested? I doubt the problem is isolated to the starter, but you never know. Hope that helps! Jim

I do not think the battery was disconnected prior to the work. What happens in that case? I think it went into anti theft mode and needs to be reset. Yes to all grounds hooked up, everything clean in some cases new, and tight. Starter has been tested twice and everything is fine there.

A number of things could have happened. The BCM could have been fried by a hot wire touching something metal, for example. If you think the security system is involved your best bet is your local GM Dealer. There's no reset and the relearn procedures that everyone talks about won't work for your situation. Hope that helps! Jim