Wondering if anyone has any insights into what is causing this extended, since Tuesday 3/17/20, outage along the San Francisco Peninsula. It includes at least San Mateo, Foster City, Burlingame, Hillsborough, Redwood Shores, and Millbrae. That's as far as I can see on the Comcast map. I have at least 10 text messages saying the outage will be fixed in the next four hours or so dating from Wednesday. The error on my TV screen is RDK-03003. It's almost impossible to reach a live Comcast employee. When I finally did around noon 3/21/20, she could not tell me what was wrong. This is the longest outage I can remember in the eight years I have been a customer and comes when the COVID-19 virus has us in lock down mode and all other entertainment modes closed. The Xfinity beta stream app does not work that well and my wifi signal is not strong enough where my TVs are located to support streaming it through the Internet.
Please see https://www.xfinity.com/support/articles/x1-errorcode-rdk-03003-unable-to-connect-to-xfinity-tv. The symptom might by caused by a bad cable box or a problem at Comcast (check https://www.xfinity.com/support/status/, 1-800-Comcast voice response, or the "My Account" app), but is most likely due to a poor connection between the box and Comcast's network, usually in or near your home.
Troubleshoot by checking all connectors for corrosion and tightness, and by looking for damaged coax cable. Running the cable through a surge protector, a defective splitter, or too many splitters can cause signal problems as well. If there is an amplifier in the line make sure it's getting power. You might also try unplugging the cable box/DVR/digital adapter power cord for a minute or so.
If you can't find the problem, call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. Ask them to check the account setup and send a refresh signal to the box. If they can't fix the problem remotely, insist they send a tech out to identify the cause and correct it.
If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast cable box/DVR/digital adapter or anything outside your home, you shouldn't be charged.