telephone

user_5qpxmi here are a few steps you can try to take: 

Check Call Blocking Settings

Log in to your Xfinity account: https://www.xfinity.com/myaccount
Go to Voice Settings → Call Blocking
Review:

Anonymous Call Rejection (blocks calls without caller ID)
Selective Call Rejection (blocks numbers you added)
Nomorobo (spam call blocking service)

Turn off or adjust as needed.

 

Disable Anonymous Call Rejection

Dial *87 to disable.
Dial *77 to enable.
If enabled, calls without caller ID will be blocked.

 

Check Nomorobo

Log in at https://www.nomorobo.com
Review your settings and whitelist any legitimate numbers.

 

Restart Your Equipment

Power cycle your Xfinity Gateway or modem.
Unplug for 30 seconds, then reconnect.

 

Test Incoming Calls

Call your home phone from a mobile device with caller ID ON and OFF.
This helps confirm if Anonymous Call Rejection is the issue.