I am having the same issue. Intel Pro, iTunes 11.4, iPhone 5, updated to iOS 9.02, same message.
Seems that APPLE is just more and more ignoring its users. No use trying to downgrade by downloading any ipsw-files or reinstallign - from any internet websites as Apple has closed its signature and so the files are rendered useless. I spent hours to reactivate my iPhone, no way.
Apple is this way casting out all users that are not willing to upgrade and buy their latest products. But you guys forget that we already had spent hundrets of dollars for your fancy stuff which now is no more usable. Wow, this is the "new Apple world", thank you Mr. Cook.