I know this is way off topic but I just spent a lot of time trying to fix this so I thought I’d post this solution somewhere for others.
This is as of September of 2016, Windows 10. This applies to the iphone and itunes and the problem is that when you plug the iphone or ipad into the computer Windows does not see or recognize the device and does not sync.
I plugged my iphone into my computer and opened itunes and there was no sync. There was also no iphone listed as a device like usual.
I tried a different USB port, plugging directly into the computer, restarting the computer, restarting the phone, uninstalling and reinstalling itunes, removing the iphone from the Device Manager list and reinstalling, resetting the network settings on the phone, deleting the lockdown directory from ProgramData, and even a different cable. Nothing worked.
I could see the phone through Windows Explorer and access the pictures and videos but itunes could not see it.
Eventually I realized that in the device manager under Universal Serial Bus Controllers “Apple Mobile Device USB Driver” was missing.
Open Windows Explorer (or sometimes it’s called File Explorer)
Go to C:\Program Files\Common Files\Apple\Mobile Device Support\Drivers
In there you should find usbaapl64.inf
Right click on that file and choose Install.
A few seconds later everything should start to work perfectly. You would think that this would have been done when I uninstalled and reinstalled iTunes but for some reason it was not. In fact, I don’t even know why it was suddenly at some point uninstalled since I have never touched it or even known it was there, but Windows 10 does some strange things so…
Hopefully that helps someone, or at least helps me again in the future when I forget!