Why Is My Computer Is No Longer Authorized To Work With Purchased Items On My iPhone? Here's The Answer.
It’s saying that your purchases aren’t authorized for that computer. You have to sign into iTunes with your Apple ID that is associated with purchased items for it to authorize syncing. At the top left of iTunes, there is a menu selection for Account, then find Authorizations and choose “Auhorize this Computer”. Signing in is not enough.