cannot sync ipad because pc not authorised
I have Widows 10, two iPads and two iPhones all running iOS 9.02.
- One iPad gives an unkown error -52 when I try to sync it.
- iTunes can't see the music on the iPad, except for part of one playlist.
- All the tracks have been purchased with the same Apple id.
- All the other devices sync normally, only this iPad fails.
- If I try to sync it, I'm told it can't be done because the computer is no longer authorised for music on this iPad.
I have tried everything suggested around authorising computers on the support site, but nothing has worked so far.
Can anyone help?
iPad Air Wi-Fi, iOS 9.0.2, Windows 10, iTunes 12.3.0.44