I have cleared cache and cookies and it still does not work.
did you have a previous account that used ths same username that you use to sign in to the streaming site?
This is the only account that I have had with Xfinity.
did you try accessing stream TV using a smart device (phone/tablet) to see if the username is working at all?
I can verify that the login and the app works fine on my tablet, but not on my pc or laptop.
a comast employee will have to check the provisioning problem on your Roku. they will normally respond within 72 hours of your initial post.