Have 2015 Sierra. Intelilnk screen won't recognize usb or sd inputs. Worked fine till today. media button will go to xm, am, sirrus, and blue tooth. When push for usb and sd shows no artist input available. It is like it can't read those 2 input sources? All other things Nav, backup camera, etc work fine. Anyone ever had this problem? suggestion on fixing it?

Have you tried multiple USB sticks that are known good?

If so, I'd start by disconnecting the battery for a half hour.

Pull the system fuse for half a minute and replace. You'll lose your presets but it'll reset the system. You'll lose them and everything else by doing the battery. It'* a choice.