Thanks for letting us know all that you've done. We appreciate the troubleshooting steps you've done so far to try to resolve the issue with Xfinity Stream.
Please make sure to restart your Roku device after removing the channel and before adding the channel back to ensure the process is successful.
In addition, some channels and services can be restored by performing a system update. You can check for a manual system update by navigating to Home > Settings > System > System update > Check now.
We'd also recommend refreshing your home network connection by rebooting your wireless router and/or internet modem if you are experiencing an issue with a channel loading content.
This should resolve the issue you are experiencing, however, if the issue is still unresolved, please reply back and we will be able to assist you further.