How to Troubleshoot iPhone Sync, Computer, or iTunes Issues
If you’re having problems syncing or your computer doesn’t recognize your iPhone when you connect it, you can try some of the following steps to resolve issues that involve synchronization and computer–iPhone relations.
Recharge your iPhone.
Try a different USB port or a different cable if you have one available.
It doesn’t happen often, but occasionally USB ports and cables go bad. When they do, they invariably cause sync and connection problems. Make sure that a bad USB port or cable isn’t to blame. And check all plugs, connectors, cables, and adapters to ensure that they’re properly inserted and seated correctly.
Apple has used the same USB cable for iPods and iPhones for many years and also uses that same cable for iPads, so if you happen to have one of those cables handy, give it a try. Unless . . .
Unless, that is, you’ve purchased your iDevice after September or October 2012, when the iPhone 5 and the 2012 models of the iPod touch and iPod Nano were introduced. These devices all sport the new Lightning connector instead of the same USB–to–dock–connector cable. To use an old cable with these new devices requires a Lightning–to–30–pin adapter, which Apple sells for $29 or $39.
Restart your iPhone and try to sync again.
Restart your computer.
Restarting your computer can fix non-iPhone issues as well. It’s a good idea to reboot your computer before you do any kind of troubleshooting, be it with your iPhone or your computer.
Even if you have an iTunes installer handy, you probably should visit the Apple website and download the latest-and-greatest version, just in case.