I have windows 10, and itunes wont find my ipad. iTunes -> Files -> Devices was greyed out.
Google showed lot of useless information, but zeeshanmiralam solution works. Credit goes to him.
Connect your iPad to your PC
1) Launch Device Manger
2) Expand Portable devices, my iPad was listed there, and as long as you see it there, iTunes wont recognize it.
3) Right click on "Apple device" and choose update driver. Pick "Browse my computer for driver software"
4) Navigate to "C:\Program Files\Common Files\Apple\Mobile Device Support\Drivers" and select next
5) It should install the driver
6) Device manager will no longer show, Portable device
7) Expand "Universal Serial Bus Controllers"
8) You will see "Apple Mobile Device USB driver"
9) iTunes will recognize your device now.
