I did verify the credentials worked through the browser, and I was using just the username and not the entire email. I tried rebooting and that didn't help.
I finally resolved it by doing the software updates in Ubuntu, which had lots of updates (it's a box I don't update regularly), but one of the updates was an update to the chrome browser. Once the updated system rebooted, I launched the new chrome and the comcast authentication magically worked. I suspect it was something to do with the old version of chrome originally on this box.
This is what the log showed before it started working:
2019/09/06 22:56:42 [NAT] Successfully mapped port 8089 using natpmp
2019/09/06 23:03:41 [TVE] Auth starting for Comcast_SSO as channelsdvr
2019/09/06 23:03:41 [TVE] action=auth mvpd=Comcast_SSO requestor=nbcentertainment
2019/09/06 23:03:41 [TVE] Auth failed for Comcast_SSO: could not dial "127.0.0.1:44581": parse 127.0.0.1:44581: invalid URI for request
So, now it's working fine just thought I'd post this update in case it helps someone else