I've updated to iOS 8.3 a few days ago. And now in iTunes, my iPhone is clearly visible, but when I hit the sync button, it just spins its wheels for a minute and then gives me a message:
"The iPhone "Steve's iPhone" could not be synced because the sync session failed to start."
This sucks, especially when you are about to sync songs to your iPhone and use the best iPhone ringtons. Good news is that there's actually a fix for such problem. Read on to learn details.
According to Apple discussion, you can try to fix the iOS 10/9/8 unable to sync problem by forcing close all the Apps in the multitask window on your iPhone. Follow these steps to force an app to close: From the Home screen, click the Home button twice. Tap and hold on the app. When it starts to jiggle, tap to close it one by one until all cleared.
Now do a Soft reset of your iPhone: Hold both Home and Sleep button for around 10secs until you see the Apple logo then release. After it returns to Home screen, connect to sync and see if this resolves the issue.
If iTunes failed to sync after iOS 9 or iOS 8 update, you can still sync without iTunes. iAny Transfer enables you to easily sync all kinds of data to your computer. With it, you can sync video, playlists, photos, contacts, SMS, etc. to your computer and sync them back to iPhone in case of data loss. Before you get started, download iAny Transfer to your computer. The following steps will take iPhone for example.
Besides syncing your data, iAny Transfer also helps to backup and restore iOS data, which works the same way as iTunes. You can feel free to try out this function.