iPad will not SYNC and will not BACKUP

One more thing...

This iPad Air was previously used with iOS 8 and this same MacBook Pro with Mac OS X 10.6.8 Snow Leopard. I would do a weekly update in iTunes on the Mac for all apps — and then sync with the iPad to put all the updated apps on the iPad. I prefer to keep this practice, update Mac and then sync with the iPad.

Snow Leopard does NOT support iOS 9, so when I updated the iPad Air to iOS 9, I also had to update the MacBook Pro to OS X 10.10 Yosemite (several months ago) and the new version of iTunes on the Mac ... I am keeping the old (Snow Leopard) hard drive as an external USB drive, with a new internal hard drive on the MacBook Pro in order to boot Yosemite.

This SYNC problem began at that time, since the Yosemite upgrade with the new internal boot drive. Same MAC, new hard drive... There must be a clue here...

The iTunes Store says this MacBook Pro booted with Yosemite (and the new internal hard drive) has been authorized with this iPad Air.

The iTunes store seems to have trouble ever since the Yosemite + iOS9 update. I have tried to de-Authorize and then re-Authorize this Mac running Yosemite, but that does not seem to help. With the iPad running iOS 9, it is impossible to go back to Snow Leopard. SO... another Catch-22? It is all the same Apple-ID but a new hard drive and new OS and a new version of iTunes... Those are the only things that have changed. That is when the SYNC stopped working.

SO... now the iPad will no longer BACKUP and will not SYNC with the Mac. How to make this work?

The reason why I want to BACKUP and SYNC with this Mac?

I do NOT want to backup to iCloud.

So, I want to update all iOS apps on the MAC and then SYNC weekly between the iPad and the Mac, and do a FULL ENCRYPTED BACKUP from the iPad to the Mac with each major update of iOS, or every few months. I should always be ready to do a RESTORE if needed, without losing more than a week of changes on the iPad.

iPad will NOT BACKUP nor will it SYNC with the Mac via iTunes.

Problem persists through many reboots,

and several iOS updates and iTunes updates,

over several months now.

Will call Apple support today... https://getsupport.apple.com/

I have tried Wi-Fi and USB with exactly the same NON-results.

From the symptoms I think this is an Apple ID problem. Catch 22. Already authorized. Not authorized. Catch22.

From the symptoms I think this is an Apple ID problem. Catch 22.

Already authorized. Not authorized. Already authorized... Catch22.

Tried deleting all the contents of /var/db/lockdown

Now waiting to see if that worked.

Backup seems to be running... will it complete?

Backing up now: 2015-11-25 11:10

... 2015-11-25 11:20 ... 2015-11-25 11:25

Backup failed:

iTunes could not back up the iPad "Geo iPad Air"

because the iPad disconnected.

. . . via Wi-Fi ... same router... about 2 feet between Mac and iPad, and about 10 feet to Wi-Fi router.

Try again... 2015-11-25 11:27 ... 2015-11-25 11:37

SAME result. (Backup failed...)

≡≡≡

Reboot Mac and iPad.

Put iPad into AIRPORT mode, no Wi-Fi no Bluetooth.

Try USB. Charging indicator A-Okay! Connected via USB.

Try BACKUP now. 2015-11-25 11:52

BACKUP has completed A-Okay!

. . . as of 2015-11-25 12:01

Try to SYNC now....

Try to remove one app... OneNote ... APPLY.

Sync ran 3 or 4 minutes, then failed... ERROR MESSAGE:

The iPad could not be synced because this computer is no longer authorized...

Try

Store... Authorize this computer...

This computer is already authorized...

CATCH 22...

Check

/var/db/lockdown

has two files.

Deleted.

Reboot Mac, try again?

iTunes 12.3.1 is current version.

Authorize? Already authorized.

REMOVE one app...

Try SYNC.

. . . could not be synced because this computer is no longer authorized...

FAIL again. Same pattern.

2015-11-25 12:26

Ok.. now that I do have a valid iPad backup on the Mac, as of Noon today...

Encrypted backup should be 99.99% complete, right?

It should be safe to try a restore.