Confirm that iTunes 11.1 and Windows 8.1 are not compatible.
My system worked as expected today until the update of iTunes. I am now not able to see my iPad listed in iTunes but I am able to see the iPad storage in file Explorer.
I have re-installed iTunes, updated the driver, tried other USB ports all to no avail.
iPad (4th gen) Wi-Fi + Cellular (MM), Windows 8, I had to use WiFi to do the update