Comcast Network Operations Center confirmed they're aware of the issue and working on fixing it, but didn't provide any more details. If you are a Comcast customer and are experiencing issues, try switching to a mobile device with 3G or LTE data plan as that should allow you to have a video call.
Some customers have reported not being able to connect, and we are seeing higher error rates than normal in certain geographical regions. Other major websites have reported issues or downtime and this might be related to a larger event. We are investigating and will post updates as we learn more.