Q: 6th Gen Nano will not sync with itunes. I have done the factory reset so there is nothing on it.  It is identified in itunes and will go through entire syncing process but no music ever shows up on nano.

If you want iTunes to sync automatically, you need to set iPod to Sync Music.  The default setting after a Restore (in current iTunes) is to set iPod to use the manually manage method to load songs (drag and drop songs on iPod in iTunes).

Select iPod in iTunes (click its device button on horizontal bar) to show its settings screen in iTunes window.  Along the left side (in the sidebar), under Settings, click Music.  To the right, the iPod's Music settings screen is shown.

NOTE:  For anyone else reading this, any songs on iPod that are not in your iTunes library (on computer) will be lost.

At the top, checkmark the box for Sync Music; this turns ON automatic syncing.  Below that, if your music library can fit on your iPod completely, choose the option to sync Entire music library, and click Apply button.  Otherwise, choose the option to sync Selected playlists, artists, albums, and genres.  And select what you want from the lists below.  A convenient way to set this up is to create a playlist in your iTunes library with all the songs you want on iPod.  Back on the iPod's Music settings screen, under Playlists, find and select (checkmark) that new iPod Songs playlist.  If you do it that way, you don't have to select anything else.  Click Apply to sync your selection to iPod.

Going forward, iTunes keeps your iPod "in sync" with changes to your iTunes library, based on how you set up this screen.  If you set it to sync a playlist, update that iPod Songs playlist in your iTunes library (add/remove songs).  The iPod does not need to be connected.  The next time you connect it (or click Sync if already connected), iTunes updates iPod with the same changes.

When syncing (from empty to entire music library loaded), in the box at the top of iTunes window, do you see the songs steadily loading on the iPod over an extended period?  Or does the syncing process start and end quickly, after about 10 seconds?

At the bottom of the iPod's settings screen in iTunes, does the Capacity Bar show that the songs (shown as Audio) are on the iPod?

On the iPod's settings screen, in the sidebar, under On My Device, click Music.  To the right, the iPod's song list is shown.  Does it show that songs are on the iPod?

When using the iPod, how are you checking for the songs?

Sorry, I meant the iPod's settings screen in iTunes, when you click the device button on horizontal bar.  In the sidebar, in iTunes window, under On My Device, click Music.  To the right, you should see the list of songs on iPod currently.  This is to confirm that iTunes sees the songs as being on the iPod.

Earlier, when you said you, "I have reset to factory settings," was that by using the Restore button in iTunes.  The Restore button is on the iPod's Summary setting screen (in iTunes). 

Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support

If you did a "reset" on the iPod, that just restarts the iPod.  There is also a Reset Settings command on the iPod, which does "reset to factory settings."  However, that command does not erase the iPod's storage and reinstall its software.  The Restore button in iTunes does that, so if you have not already, you should do it.  This problem sounds like data corruption on the iPod storage, or a problem with its software.  The song files may be on the iPod (according to iTunes), but the iPod's onboard software is not seeing it.

The Restore button in iTunes does the full "factory reset."  And it sounds like you did that, and that should fix a data corruption problem and a software problem.  So normally, if a Restore does not fix it, the cause is likely to be a hardware-related problem.  But this situation is odd...  You just did a Restore, and iTunes treats the iPod normally, clearly syncs songs to it and shows it has songs on it (after it finishes syncing).  But when using the iPod, there are no songs.

Was this iPod was working properly for you before this issue occurred?  One day, after syncing, it showed zero songs?

Do you know anyone with a Mac?  I'm thinking, do a Restore using iTunes on a Mac, which reformats the iPod for Mac.  Then, connect it to your Windows PC.  iTunes should prompt you to do a Restore, because Windows cannot access the iPod if formatted for Mac.  This Restore (on your PC) reformats the iPod for Windows.  The aim is to get the iPod's storage reformatted, not just erased.

If that's not possible, you may be able to simulate the same thing by using Windows to reformat the iPod like it's a USB flash drive.  You may need to put the iPod into Disk Mode first

Putting iPod into Disk Mode - Apple Support

Connect to computer with iTunes not running.  Use Windows to reformat the iPod.  If FAT32 is a disk format choice, use it.  If there is a choice to do a fast format, choose to do a full format instead.  After it completes, the iPod is completely blank; to reinstall its onboard software, you must do a Restore on it using iTunes.  After the Restore completes, sync some songs again to see if there is any difference.

I use a Mac.  I did an Internet search, and this was the most understandable guide I found, for formatting a drive using Windows 7

http://pcsupport.about.com/od/windows7/ss/format-hard-drive-windows-7-tutorial.h tm

For Step 4, the Volume Label (name) does not matter, you can just call it "IPOD" (it will get renamed when you do the Restore in iTunes).  For Step 5, that's where you choose FAT32.  For Step 6, use Default.  For Step 7, uncheck Perform a quick format. The rest is clear as written, but if it's not clear to you, you may not want not do this...