Xfinity Stream app not working on Roku

We have had xfinitity for several years and use the xfinity stream in other rooms. However, the xfinity stream app on Roku is not working...the error message it says states "Run into a problem while streaming <insert TV program> and attempting to resume." This has gone on for a few weeks. We have tried restarting the Roku devices, uninstalling and reinstalling the app itself, to  no avail.