Back on earlier betas, if I changed profiles (iTunes accounts between Canadian and US iTunes stores), it would remove the Watch Now and show the "try again later" message. During this time, in the app settings, it wouldn't show any apps linked to the tv app either. Nothing seemed to fix it (rebooting, restarting the app). Oddly enough though, going into the music app seemed to reset something and the Watch Now would load up again. Since the public release, this hasn't happened anymore, but back when it did, going into the music app fixed it every time for me