I believe this particular broadcast is blackout on the steam app service because it's is a pregame of a rsn. Did any other channels work?
I mean, it makes sense. The Xfinity Stream app is a perk given for customers for subscribing to their Internet and /or cable service. I used to have the mobile stream app for them on my phone and it never worked while I was on my college campus either.
This just happened today for me. Is there a workaround? I've been using it with a network other than Xfinity and been working fine.
You could setup PiVPN at your house. When you connect to it while away the Xfinity Stream app will think you are on your home network. I've been using this way for about a year.