If you're experiencing or seeing this error, please try the following 2 items:
1) Clear your browser cache.
2) Go to http://tv.xfinity.com and try logging in there.
Additionally, please try the other troubleshooting steps we have posted: Tips to fix most issues!
If you're still experiencing an issue with loading the XFINITY Stream player, please submit a ticket to the XFINITY On Campus team.