One day I found I could no longer transfer files between my iPhone and iTunes.
Normal procedure would be to connect the phone to my laptop using a USB cable, and then in iTunes go into the Apps part of my phone, scroll down to File Sharing, and I’d get a list on the left of apps which had file sharing capabilities. Then I could click on an app, and in the section on the right I’d get a list of all the files which I could save from that app.
For some reason this stopped working – I have no idea why – I didn’t change any options myself. I’d go into the apps screen, see the apps on the left, but clicking on them no longer brought up any files on the right. And the “File Sharing” title turned to “File Sharing is Off”.
Solution? Not sure why, but turning wifi off on my phone seemed to make it work again. Turn wifi back on, files disappear. Turn wifi off, files come back.