This worked for me as well. What was key though was re-booting the Xfinity Modem, not necessarily the router as that did not fix for me. It’s key that you re-activate the Xfinity account through the xfinity site with the code as part of the process. All other attempts without that step failed for me.
The fix described above worked for me on March 27 (for several days when trying to start the Xfinity Beta channel, it would stall at "initializing" and never open the channel. Here is what I did:
1. Uninstall the Xfinity Beta app from the Roku TV and turn it off.
2. Unplug both modem and router, wait 20 seconds, plug them both in and let internet reconnect.
3. Turn on Roku TV, install Xfinity Beta app. It then required me to reauthorize my Roku by going to xfinity.com/authorize and entering the code that was on the TV screen.
This fixed it.
I tried this (sort of). I uninstalled the xfinity stream beta app from all of the TVs. I did a reset of the modem by holding in the reset button on the back. Waited until it came back up. Reinstalled the app on one of the tvs. Still not working!!! I am now on hold with xfinity again for the 3rdtime in 2 days. Should I have unplugged it? Would that make a difference rather than just resetting? All my other apps (Netflix, Prime video, etc.) are all working. Please help! I am beyond frustrated with this issue.
Thanks! I will try again tomorrow. I am beyond exhausted with this at this point in the day!! I will let you know if this works...