This is an issue that will likely only affect a small number of users. But since it was an problem for me, it worth a post to explain the fix.
One of the great new features of iOS 5 is the ability to sync with iTunes over Wi-Fi and eliminate the need to plug the iOS device directly into the computer in order to backup and update software, content and playlists. To enable this feature, first plug the device into the computer via USB. When it appears in the Devices list on the left side of the main iTunes window simply click once in your devices icon. Then select Summary from the top of the main window on the right.
Scrolling to the bottom of the main window, there is a section labeled Options. Be sure to select the box labeled Sync this Device over Wi-Fi. Until that box is checked, the iOS device will not sync over Wi-Fi. If the box was already checked by default, you’re set. But if you had to check it yourself, be sure to click the Sync button in the lower right hand corner of the window. This insures that the settings take effect.
Apple’s documentation explains that iOS devices should auto sync with iTunes when the iOS device and the computer running iTunes are located on the same wireless network. The auto sync is supposed to kick in shortly after the iOS device is plugged into a power cable to recharge. But in my case this sync was not kicking in automatically. I had to engage the sync manually.
To kick off the sync manually from the iOS device, open the Settings App, select General, and then select iTunes Wi-Fi Sync. If the devices in on the same Wi-Fi LAN as your iTunes computer and that computer is booted up and running iTunes, the Sync Now button should be enabled. If it is not, then there is an issue either with the Wi-Fi, the host computer, or iTunes. Again, be sure that the Sync Over Wi-Fi box option described above has been selected in iTunes.
So, why was my iPhone not auto syncing with iTunes when plugged it into the power adapter? I could initiate the sync manually so I was sure it was not an issue with my network. It turned out that there was a setting in the iTunes preferences that was blocking the auto sync. It was new with the release of iTunes 10.5.
Open the iTunes Preferences and click on the Devices icon at the top of the window. Simply uncheck the box labeled Prevent iPods, iPhones, and iPads from syncing automatically.
That was it. Simple fix. The next time I plugged my iPhone into a power plug it kicked off a sync with iTunes over the Wi-Fi with my MacBook Pro that was located on the opposite end of the house.
Wi-Fi sync is a simple feature, but everything has to be just right in order for it to work. I’ve covered just a few things that can go wrong. Some of the more obvious issues are less easy to troubleshoot. First of all, make sure the iOS device is on the same network as the computer with witch it will be syncing. And, of course make sure the computer is on, awake, and has iTunes running. The ins and outs of many of these problems, particularly the many potential wireless issues than can arise are beyond the scope of this post. But it is my hope that some of the info here will help a couple of readers solve the same issue that had me stumped for a short time.