Xfinity Steam App Error TVAPP-00287, via Roku Ultra

We have been running the XS app on 2 Roku Ultra and 4 Roku Premier devices since August 2020.

In the last two weeks, the app had started to buffer &/or show a "Cannot be played" message on a devices.

Starting yesterday, we are getting error code "TVAPP-00287"

All other streamers, on not just Roku but on our other devices, work, as does the internet itself.

We tried deleting the XS app to reinstall but, when we find it in the roku app store, it only lets us Open the app, with no option to add to home screen.

Any assistance would be appreciated

[Edited: "Personal Information"]