Thunderbird isn't accepting my old password so I can't enter my new comcast password

This is a Thunderbird question so be patient :). All of a sudden I was locked of MyMail and Mail on iPad and iPhone so I updated my comcast password but I can't update it in Thunderbird because it isn't accepting my old password. When I try to send a message there's a window that pops up that says why it wasn't sent and it says enter new password but when I click on that it goes away and doesn't let me enter one. When trying to figure this out I googled and it suggested removing all providers if I wanted to use all new credentials. So I have to add Comcast back in but I don't know how. So now it doesn't give me the option to show passwords. So i screwed up. How do I straighten this out? Plus it is now almost midnight and I have not received any new emails since this morning. I think part of this is the business about having to change to a new Comcast email system. But I still need help with the password issue. I have an appointment with Comcast tomorrow afternoon so hopefully I can start to get emails in MyMail. TIA.