I have found the way of watching NOW TV though the Apple TV. when you go into the NOW app on the Apple Tv box, go across to settings - mine said I was still logged in even though I couldn't access the programmes. Log yourself out, come out of the N...
Thanks for raising this issue, I have the same problem, everything up to date including my monthly subscription directly to Now TV (not via iTunes), no longer able to watch via Apple unless I subscribe again.