Xfinity App shows no Internet Connection but I have Wifi with new modem/router

I disconnected my Xfinity Gateway Modem/Router as it is no longer included free in my service plan. I added an approved Xfinity Wifi cable modem (Arris Surfboard SBG8300) via the Xfinity mobile app and I am able to connect to the Internet. But when I check the Xfinity mobile app, it states "Your home internet is offline".

Two questions:

1) How can I get the app to recognize that I am online

2) My plan is to return the Xfinity rental Gateway modem/router. How can I delete my wifi name and password from this rental device.

Thank you.