Don't know if this will work, but it worked on my 5th gen Ipod.
Plug it in to your to your Mac or PC via usb cable. Open iTunes. Then Hold the volume down and the sleep bottom until the Nano reboots. If it still doesn't appear on your iTunes but it does appear on your desktop, then there is a problem with your firmware. You may have to find the firmware on the web or look it up in youtube.
Hope that helps. Have a good one.