Today I was trying to get to use the My Account iOS app and it would time out logging in. I tried to log in at the Comcast.com web site, but it would time out going to login.comcast.com on multiple devices. Finally I used my iPhone and turned off Wifi so it used LTE and I could access login.comcast.com and login.
Basically login.comcast.com never responds on my Comcast internet connection, but it does over LTE. I haven't found any other web sites with the same problem. Comcast used to work at home as of last week.
I've had that issue occasionally. Rebooting the modem usuallyhelps. I think some maintenance or other can cause it to lose some of the information needed to authorize your connection to the servers, or at least it gets out of sync until there is an update.