incoming phone calls displayed on TV.
You must have CallerID to the TV enabled as a feature. If you already have the feature and it isn't working see below:
See this for X1 https://www.xfinity.com/support/cable-tv/x1-text-messaging-notifications/
Or this for legacy cable https://www.xfinity.com/support/phone/settings-for-the-universal-caller-id-to-tv-app/
If the above does not help, call into Comcast at 1-800-266-2278 or 1-800-934-6489 and speak with a CSR to ensure the CallerID Rate Code is active on your account.