Xfinity Streaming App on Roku forgets authentication failure

When I add  the Xfinity Streaming App Channel to Roku and then authenticate for my account using the TV code, the app works fine for a few days and then with no change in settings fails. I have to remove the App from Roku, reinstall and then go back to the xfinity web site with the device authentication code. I have already done this about a dozen times over the last few months. This NEVER happens on other instances of the app installed on an Ipad or an Android phone. How do I fix this?