Wifi sync not working on iPhone 5s with iOS 8.0.2

Question

I have an iPhone 5s with iOS 8.0.2, and iTunes 12.0.1.26. Sync via wifi doesn't work (with one partial exception[1]). USB sync works fine, but when the phone isn't physically connected via a USB cable, iTunes doesn't know it exists. On the phone, in Settings/iTunes Wi-Fi Sync, "Sync Now" is disabled and it says "Sync will resume when '[my computer name]' is available". It's got the correct computer name.
In the online help, I find the following claim:
When the computer and the iOS device are on the same network, the iOS device will appear in iTunes.
In my case, the computer and the iOS device are on the same network, and the iOS device does not appear in iTunes. I had a previous iPhone 5S which was able to sync via wifi to the same desktop computer on the same network. That one may have been iOS 7 (I can't check because it tried to learn to swim).
The checkbox in "Summary" is checked:
I tried unchecking it, applying, checking again, and applying again. I then restarted both iTunes and the phone.
[1] Partial Exception: I found an "answer" on here where you turn off three different random features on the iPhone, turn them back on, reboot the iPhone and the computer, and then WiFi sync does actually works -- exactly once. Now it's disabled again. All that fussing around was enormously more hassle than just finding a USB cable; if I wanted to spend half an hour performing 10-second tasks I'd have bought another Motorola product.
Is there a solution that works permanently, or do we just wait for a fix in a future OS revision?

Answer 1

On your iPhone 4S go to Settings > Wi-Fi. Click on Wi-Fi to both disable and enable it. If you are still unable to enable this setting it may be possible that the iOS7 update did not take properly.