Trying to watch a program via the app and says in home only. I own my own modem so is that only a feature with Comcast provided equipment.
If you are connected to your own wifi SSID and not Xfinitywifi SSID then you may need to use the Xfinity My Account app. on the my account app, select the internet 'tab' and verify that your modem is listed and that the MAC address on the my Account app matches the MAC address printed on the label on your cable modem.
My devices does not list a modem at all.
contact billing department at 800-Comcast and ask the representative to verify that your modem is assigned to an 'outlet' on your account.