AT&T Note 3: KitKat finally!

Hello everyone. I bought a note 3 from a person on CL. He told me it was rooted but he unrooted it for me and took it back to stock. But the official kitkat update will not install. I get the install interrupted message. Is there any chance that this phone was not unrooted correctly? Is there somewhere on the phone I can check if it is rooted? FYI the baseband is N900AUCUBNB4.
The build is JSS15J.N900AUCUBNB4. Any help would be greatlt appreciated. Thanks.