Why does my iTunes isn't longer showing iPad Air available for wifi sync?

[TheGenerous]

Can't sync iPad Air over wifi with iTunes.

A few weeks ago whenever I launched iTunes it will take a few seconds and show a button to sync iPad Air over wifi. Now is not shown and I can't figure out why. Please help.

OS X 10.9.4
iTunes 11.3.1 (2)
iOS 7.1.2 (11D257)

In the iPad Air --> General settings, iTunes Wi-Fi, I press sync and begins searching but does nothing.

Thank you

 

[t0mat0]

Is the iPad plugged in so charging, also are they on the same network?

 

[TheGenerous]

Is the iPad plugged in so charging, also are they on the same network?

Thanks for replying. iPad is charged, and both the Mac and the iPad are on the same network at home. Previously I could sync with out the need for plugging.

 

[Bruno09]

You might connect the iPad to the Mac via USB, then toggle the "Sync with this iPad over wifi" tick box.
Click "Apply" in the bottom right corner of the window.

Then unplug the iPad, it should "stay" in the side bar of iTunes.