There is a link on the "subscription required" popup window when I tried to watch something (from a channel that we receive, so this is confusing). The link is xfinity.com/tv-movies. That link redirects to http://xfinitytv.comcast.net/-movies when loaded, which leads to the "can't find that page page."
Which links to here to report a broken link. I don't know why a broken link should be on the forum, but here you go.