IPod Touch 4th Generation issue - no longer able to view Device in iTunes? I can't add, Sync, Back Up or Restore?

Question

The PC’s I use have Windows 7 installed along with the latest version of iTunes.  I have
previously deleted all components of iTunes and re-installed.  This made no difference. The PC’s do not recognise my iPod in the Windows Device Manager using ‘devmgmt.msc’.  and still nothing in iTunes.
Also C:\Program files\Common Files\Apple\Mobile Device Support\Drivers / - do notlist ‘usbaapl64’.
The folders listed are ‘usbaapl.cat’, ‘usbaapl.inf’,‘usbaapl.sys’ and ‘usbaaplrc.dll’. 
Whether this makes a difference I do not know.
iTunes doesn’t recognise my iPod either however it recognises my attached iPhones OK
(iTunes/File/Devices) with the options of Sync; Transfer Purchases and Back Up being available. 
When my iPod is connected, iTunes shows the File ‘Devices’ sections as being inaccessibly greyed out. 
So to reiterate, I have tried multiple computers and a variety of Windows operating systems (but I’m running Windows 7) with absolutely no success; the ‘Device Manager/Universal Serial Bus controllers/Apple Mobile Device USB Driver’ appears with my iPhone but nothing for my iPod; the Apple Mobile Device Support is installed;  all my USB cables work OK; the device does not appear in Windows or in iTunes; iTunes has been fully uninstalled and reinstalled; the version of iTunes is up to date; the iOS of the iPod Touch shows it is up to date at version 6.1.6 (and cannot be changed) and even a hard reset has been tried.  Everything tried and suggested with complete failure.
I can use a USB port to charge up my iPod and can still receive e-mails, updates to apps and can play songs but I can’t add any new songs or update iOS.  There are no error codes because as far as the computer and/or iTunes is concerned, there is no connected iPod. My iPod used to work perfectly.   Also I tried the Apple iPod forum without success and was advised to try the iTunes community support.
Please help!  Thank you.

Answer 1

I'm having the same problem with my 4th gen iPod touch. After the update my iPod synched and wiped all my music off - apps & podcasts weren't affected. Restored it a couple of times and that didn't work.
I tried copying a couple of albums over and it would do a couple of songs then the rest of the album would look like it had copied instantly. I tried playing the songs and it would play the first couple of songs once, then it came up with ! Beside every song (including the ones I'd just played and said they weren't on my iPod.
I've removed iTunes from my laptop and downloaded the few iTunes bought albums over WiFi to my iPod. The rest of my music is from cds or mixes/podcasts downloaded from soundcloud so I've had to use a different program to copy some of this music to my iPod for the time being until I can see how to sort this out.