Hey man, I just had the SAME exact problem, except I'm not using a Mac.
-BUT, connect your phone.
-Next click on your phone name on the left side of the screen where it shows the phone icon.
-Next at the top where it says "Summary, Info, Apps, etc.." click on music.
-Then make sure the box that says "Sync Music" is CHECKED, then just click Apply and/or Sync.
This then put all of my music that was in my library onto my phone. If this somehow doesn't work for you, then I don't know what the deal is but all I can say is just to try restoring a recent backup? If this does work, please reply!
I've tried this unfortunately. Thanks anyway though.
I tried selecting to sync music manually, clicked the little triangle next to the iphone logo in the sidebar, selecting music and clicking 'autofill'. I get the message "iTunes cannot add any songs to the iPhone because no songs in your iTunes can be copied to this iPhone".
Think it's well and truly broken, might have to go into apple store soon!
It hasn't worked for me either. Now i'm left with no music, and the factory reset has been very inconvenient in that most of my settings and preferences are wasted.
I've arranged another phonecall with apple tomorrow. Looks to me like there's a bug with iTunes being able to work with the new software update, or vice versa. At least we know it's not a hardware fault... I'll keep you updated if I can find a fix!
Alright, re-installing iTunes worked for me. However the factory reset I was asked to do beforehand has me in the same boat. All my logins are gone, all my app saves. I have games like Final Fantasy in there so a lost save is devastating. Not really happy with the order they had me troubleshoot things.
Thanks Zach, that managed to clear things up for me as well.
I uninstalled here: http://appleheadlines.com/2011/07/12/how-to-uninstall-itunes-on-mac/
It's pretty annoying having reset to factory... Lost all app data like you said, and everything's different. The 2 phone calls with support didn't help, just made things worse. They didn't suggest an iTunes re installation either.
I just encountered the same problem. Only when I click the "sync" button it goes through the sync process as it should. I recently added a few songs to the library and they just would not add to my iPhone 4S. After reading through this post I made sure everything wash "checked" as they should be, and they were. So I "un-checked" the boxed and "checked" them off once again only to notice my entire music library had disappeared (Luckily I don't use iTunes to save my songs). I had to re-locate the folder under "Add folder to library.." on iTunes and it was fixed. I've had nothing but problems with iTunes and am kind of getting fed up with it. It constantly freezes up with the same responce of "Not Responding..". My music library randomly disappears along with all my songs ratings (I use the ratings to easily sort my music without having to create a playlist), so it really is a pain in my a55. As much as Apple would hate to hear it, I never had a problem with my Galaxy S2, nor my HTC I had before that
And just a completely un-related side note, I called tech support the other day because my girlfriend couldn't create an iCloud account on her phone. It kept saying the maximum number of accounts had been created on the phone. I did what everyone here does as well.. I searched the internet and found that if I called Tech Support they could simply allow a creation of another account on that phone. So, I followed the advise and called Tech Support, which put me on the phone with somebody who could barely speak english. I told them what was up and they said that I must purchase an extended warrenty on my phone in order to fix it, at which point I told them to forget it and that I'd create an account on my phone and my girlfriend could simply just log in to it from her phone. Tech told me that it could not be done and that I would certainly have to pay for them to fix it on their end. So I told them to nevermind, and that I wasn't going to worry about it. So now he says I'm eligable for a free $100 Apple gift card/ discount card.. which they later tried to SELL me for a nominal fee... But anyway, my solution worked with creating an account on my phone for her to log in to... I'm beginning to lose interest, and respect for Apple do to the amount of unnecessary issues I've been faced with recently, especially the VERY POOR tech support that outright lies to you over the phone in order to make a buck. (I own an iphone4 and two 4s's and also purchased my girlfriends iphone4. I hope Apple reads this and realises that they could be losing a valuable customer (more than likely not just me) and a LOT of sales over this re-occuring nonsense.)