I posted in an answer in a different thread earlier today that may be useful to you: http://forums.xfinity.com/t5/Stream-TV-App/Problem-with-Watching-Recorded-Content-on-iPad-Pro-since-...
If, as your handle implies, you are in Boston, the problem described in the second bullet in that post is actually still going on. Teams are working on fixing the root cause of the issue; in the meantime, the workaround described in the first bullet may help. I'm sorry this is happening. :-(