Xfinity app on my phone suddenly showing "Home internet is offline". But it isn't! My home internet is quite definitely online!

I never had this issue before. It cropped up quite suddenly, for no apparent reason.

I tried signing out of and signing back onto the app on my phone. I tried dumping the app's cache. I tried turning my phone's Wi-Fi on and off. Nothing worked.

I own my own modem (AKA, "customer owned"). I even tried turning that off and on. Didn't make any difference.

The only things that have changed recently are that Xfinity has upgraded the neighborhood's fiber optic network and that I have purchased a new Samsung Smart TV. I have not tried to connect my phone with the TV.