Q: the iPhone could not be synced because this computer is no longer authorised for purchased items that are on this iPhone

Awesome! thank you worked for me as well!

check it out guys. it will help!

http://macs.about.com/od/appleconsumersoftware/qt/Problem-Authorizing-Itunes-To- Play-Purchased-Music.htm

THANK YOU!!!!!! I DID!!! WHOO-HOO!!!!

I just closed and opened again the iTunes and worked for me...

i have the same problem on iphone 4 running ios7.1.2 on Windows 8.1 64 bit. I have tried authorizing and deauthorizing but there is no solution yet.

Its easy, just click file in tunes and go to devices and choose "transfer purchases from .......". Simple, worked for me!!!

Thanks a lot InsaneInc, it actually solved my problem after deleting the apps that I had downloaded with my old apple ID, now I am able to Sync my apps to iTunes again

Guys if anyone is having the same problem then please refer to InsaneInc comment!

Stay humble

VIP1992 Delete the apps that you have downloaded with your old apple ID and reinstall them with your new apple ID it will solve your problem!

I had this problem too but not for long. This started when I restored my brother's iPhone backup on my iPhone. Whenever I wanted to sync my phone(5S), I would get the perinnial 'computer not authorised' loop.  Even the deleting the iTunes option did not  work as you can delete iTunes from Mac( your OS will need it). I was so fed up to a point that I wanted to get the MAC rebuilt.

Eureka moment: I did not realise that applications purchased from my brother's apple ID were sitting in my phone. The moment I deleted them and had no application purchased from his ID on my phone, I was set. I tried to sync my now and viola! synced all my data. Please let me know incase you folks out there need some help.

I had the same problem, I later remembered that I recently downloaded some apps to my iPhone from my GF's apple ID. I then authorized my computer with her Apple ID and from then on, the iPhone synced normally.

I had the same problem after purchasing my new iPhone 6 but was able to fix it without editing any content.

Point of note here: I have one Apple ID for iCloud and another for iTunes purchases. I keep iTunes logged in under the second Apple ID.

During the iPhone 6 set up process I entered my iCloud Apple ID. All my relevant iCloud data was restored on the phone such as contacts, emails, calendar etc. Apps, even though they were purchased using the iTunes Apple ID, were also restored because they were captured as part of the one iPhone cloud backup.

Also on my phone were the newly installed Pages, Keynote, Numbers, Twitter apps. I assume it was done as part of iOS8 to save chewing up a users bandwidth by having to download them separately.

The stated error occured when I attempted to sync/backup to iTunes over cable (Macbook Pro 13" Retina). However the back up attempt produced causes for the error stating that the newly installed Apple apps were not authorised.

I can assume two things. One is that the new apps were linked to the iCloud Apple ID upon phone setup. And two, that the computer detects the apps have been purchased with a different Apple ID to the one iTunes is logged in with, and deems them not authorised for the computer.

I simply deleted the offending apps from my phone leaving only those purchased with the one Apple ID (the one which iTunes was logged into) and the sync/backup occurred with no problems.

The ideal solution is to have one account for all purchases. Failing that, authorise the computer for each Apple ID where purchases have been made on the phone.

I had the same problem. Here's what worked for me: In iTunes, under "Summary", I selected Automatically Back Up >THIS computer. Then, below that, under "Options", I ticked the box "Automatically Sync with this iphone is Connected".  Click "Sync".  Problem solved. 

under windows (xp): New iphone6+, had to upgrade iTunes, then it wouldn't sync with the infamous non helpful dialog box message.  Did a backup which, unlike doing a sync, coughed up a dialog box showing all the apps it wouldn't sync.  Crazy.  All the apps were purchased on the same iphone with the same account but for some reason it had an issue with a bunch of them. ***?!  I deleted those apps from my phone and did a sync which finally worked.

Note, I think I did a "restore from backup" which perhaps I didn't need to do as I recall that it was during the backup that I got the list of "offending" apps.  I could be wrong about that.

Anyway, dear Apple, **** you!  Seriously, it took a solid hour to install the new iTunes.  Jesus.  I thought the install had frozen on multiple occasions and then to have my first 1.5 hours of this product involved in hunting down this asinine sync issue, a google snipe hunt, with no definitive response from apple.  Honestly, if this was my first apple product, I'd have returned it.   Reputations are ruined this way and once ruined it can take a long time, if ever, to come back.  Just outrageous.

I was having this same problem with apps after my iPhone 6 plus got replaced under warranty.

I had 141 apps installed on my iPhone - they were marked as the following in iTunes:

"Will Install" for apps that had been installed on my old phone (and in local backup).

"Install" for apps that were not installed on my phone (but still listed in iTunes).

"Remove" for apps that were currently on the new phone (such as iTunes U, etc.)

I ended up marking some apps as "Install" - so they wouldn't load. Then the sync started.

Perhaps one or more of the of the apps was now defunct or pulled off the iTunes store - or was corrupt - or loaded with my iCloud ID instead of my iTunes/Apple Store ID.

I'm not sure - but it seemed to solve my problem. Hope this helps someone else.

For me, this was because I enabled family sharing and grabbed some of the apps my wife had purchased, but didn't have both accounts authorized for the computer that was syncing.  After authorizing her apple ID everything worked fine.