NBC sports regional websites

According to this page: https://www.xfinity.com/support/articles/tv-everywhere-csn# "If you are an Xfinity TV customer who has NBC Sports in your channel lineup and reside in one of the regions below, you can live stream local sporting events simply by visiting your respective regional NBC Sports website"

I am able to access NBC Sports in the Xfinity TV service. However, when I try to confirm that Xfinity is my TV provider on the NBC Sports Boston page, I get an error message that "this network is not included in your current Xfinity TV service." It does not give me an option to enter any login credentials.