Turn off location-based charging if you don’t use Onstar. It interferes with off-peak charging if Onstar isn’t in use. Kind of an inadvertent booby trap by GM. It caught me!
Same problem-fixed it! Turned off the location-based charging. Turns out if you’re not using Onstar (which I wasn’t), having location-based charging “on” will disable off peak charging. Who knew? It’s kinda a booby trap from GM.
Turn off location-based charging if not using Onstar.