Why won't iPhone won't sync?

Hey so before the iOs7 came out for the iPhones I had the beta version installed, so I actually had iOs7 for a couple of months before it was released.
Well I went to unplug it from my speakers and I had an "Activation Required" notice pop up and it blocked me from accessing my phone. I tried putting it in DFU mode and plugging it into my computer to restore and update it but I keep getting an "Error:3004" thing pop up before I can fully restore/update it.
I took it to the Apple Store and they where able to put it into DFU mode there and restore/update it on their computers.
Well now, I have it and I want to sync my phone so I can put the Sons of Anarchy playlist on there, but I keep getting a message from iTunes saying "My phone could not be synced because the iPhone could not be found on the network"

What the heck does that mean? Is there anyway I can fix this problem?

Try downloading itunes unless you already have it. If so, the delete all things related to your iphone from thw computer. Then, redownload everything and try syncing it. Hope this helps.

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