Sorry about the inconvenience and the issues you are having.
If you are using a cell phone, ipad device etc to receive your notifications please log into your comcast.net email address and verify that your notifications are on the server. If they are try power cycling your device.
If you are still experiencing an issue can you please reply to me and let me know.
Since we got a new Comcast box our phones in the house no longer show that we have a voicemail. This worked with the old Comcast box. Comcast tech support had no idea why so they open a CR ticket number. Does anyone have any idea why this stopped working?