2016 Sierra All-Terrain Crew Cab with 6000 miles on the clock. The rear windows on both sides are not working from either the driver's or passenger's window controls. Driver and passenger side front windows work both from the driver and passenger controls. I've tried with and without the window lockout switch on, that isn't the issue. The dealer didn't have enough time to look at it extensively the other day, but they said it wasn't a fuse. Any of you have this happen and if so, what was the cure?