It is a Comcast issue, and they are working it.
We're experiencing an outage at the moment; teams are working to get everything back up asap. No need to report further—we're definitely on full alert already. Apologies for the interruption!
I am experiencing the same error too...glad Comcast is aware of this...I was on the phone for a while with the tech trying to figure this out. She finally gave me a ticket number; Comast will call me back once it's resolved.