I've been receiving the error Error TVAPP-00203 or similar for over six months which does not allow me to watch live TV at https://www.xfinity.com/stream/live. I have troubleshooted every possible way.
Comcast/Xfinity told me that this is an internal technical issue and they don't have an ETA on the fix.
This level of service is unacceptable.
I've had the same problem for weeks. Turns out that the tv cable box has to be plugged in and have the cable line to it to be able to view on computers via xfinity.com