My iPod nano 4th generation no longer shows up in iTunes or desktop.

My 4th generation iPod nano was working fine until last week. I have followed the suggestions in Support...My iTunes is the latest version 12.3.3.17, the OS is up to date. When connected by usb the iPod screen says it is connected, but randomly switches to the home screen and back again. I have reset the iPod (several times), I tried every usb port, a different usb cable and an iMac and iBook, it is not recognized by the computers or iTunes. I am able to connect my iPad without problem. Any suggestions?