I have an IPA signed for ad-hoc distribution. I can install it fine with Xcode Organizer by dragging it to the device. It also worked with iTunes <=10 by dragging onto th
For iTunes 12, drag the .ipa file from the Finder to the Apps area NOT inside your device (in iTunes)... alternately, you can just double click on the .ipa in the Finder.
Important note: you have to change Version and/or Build number. Otherwise, you get no notice from iTunes at all...
Then switch to your device in iTunes, and install or update the application.
Then hit sync.