Xfinity stream

I am having the same problem with my Roku as everyone else for the last 3 days.  I have restarted my modem, restarted the Roku, deleted the app and reinstalled and no success.  The app opens, goes to the screen for a second or two and instantly goes back to the home screen.  This is really frustrating and we are paying for a service we can't use, clearly Xfinity has not figured this out.  I go to the Comcast store for a box and they recomend a Roku vs renting a box.  Thats fine if the Roku will work.  Mine is on a Sony TV that cannot download the app so I need the Roku to work.  Doers Xfinity have a solution?????????