I can't open my email

Try clearing your browsing history/cache, then sign out of the account and back in again.

Thank you so much for reaching out! Apologies to hear about this hiccup on the email. Is this native in the browser or in a client based software? 

This began happening to me also when the screen changed to enter your username, email, or phone number and pressing let's go.  It says invalid username or password and goes back to that login screen. I didn't have a place to enter the password which has been saved previously.  I am using an updated chrome browser on Windows.  After displaying my passwords in autofill it appears that my username for xfinity begins with a capital letter.  I either never knew this or the former login screen accepted a lowercase first letter.  I never capitalize my email address.

So try to capitalize the first letter of your comcast email address when you try to login.

By the way, if you use many websites and autofill, clearing out your history or passwords may not be that convenient, until you bookmark all your favorite websites and copy all your passwords somewhere.  Really seems like a lazy solution and I dislike xfinity for saying that when you sit on the phone to talk to someone.