I updated my iPhone to iOS 12. Now iTunes won't recognize it so I cannot sync or backup. I checked my System Preferences, and USB - the iPhone shows up there when it is connected to my iMac. Everything is up to date on my iMac, running High Sierra. Any ideas how I can fix this problem?
Give this a try. This was posted by the leading authority on all things iTunes in ASC. It does work.
Workaround to allow iTunes 12.8 for Mac to see iOS 12 devices.
Download the current 12.8 installer for iTunes from https://www.apple.com/itunes/download/.
Unlock your iOS device and connect it to USB.
Install iTunes from the .dmg that you've downloaded.
At the end of the installation it should announce that a further software update is required.
Install that and iTunes should see your device and others you may have.
This last little software installation that tt2 talks about, takes only a few minutes.
This worked - thanks! Odd though, that my version of iTunes was 12.8 and no updates were listed in Software update. But all is well now.
iTunes doesn't recognize iPhone with iOS 12
