My unit worked as it should when connected to computer but was screen stuck on "ok to disconnect" or "do not disconnect" or diagnostic mode. I happened to have another iPod Nano 6th I was working on so I took out the battery/logic board and moved it to the unit with the good flex cable; and it worked flawlessly. Likely, the switches went bad with some water exposure; or there was moisture stuck in there; I replaced cable since I broke the cable trying to expose it. So if reset and restore doesn't work, test the on/off volume, headphone cable. I wrestled with restore/reset for too many hours and searched internet for hours for solution with no luck, then solved it.