iPhone and iPad don't always appear in iTunes for wifi sync, why? Sometimes, when my phone and ipad are both turned on and I open iTunes it shows "2 devices" in iTunes and I can sync. Often one or neither will show up, no matter what I do.

I can sync my iphone and ipad over wifi using itunes, but not always. In fact quite frequently neither shows up in itunes. I try to reboot them and sometimes they show up, but not all the time. I have tried rebooting iphone and ipad, the computer, checking and unchedking "sync over wifi," etc.

Nothing changes. Very often one or both do not show up to be synced. they work find if connected by usb cable, but not over wifi.

any help would be appreciated.