If you get a login issue in your Comcast Email Account, there are a lot of reasons behind showing "you can't log in to your Xfinity email account". It may be you entered an incorrect username or password and maybe your Comcast account has been hacked by someone. So, don't worry and reset your Comcast email account password and create a new or strong password, and then log in to your Comcast account.

See also - https://getassist.net/comcast-is-not-receiving-emails/