I have been using Pegasus for about 25 years. It seems that I have this problem every time I get a new computer. I just moved to windows 11 and have loaded ver. 4.80. I run the setup wizard and enter all the same data as before; pop3, user name, email address, password, etc. Here is what I have entered for pop3:

mail.comcast.net

Email: artlayton@comcast.net

I continually get a message stating username or password is invalid.

Any suggestions?

This support article shows only the name portion of the email address as the user name:
https://www.xfinity.com/support/articles/update-pop3-110-995

Notice that this article contains a link to instructions on enabling 3rd party client access to your Comcast account. We know that when this isn't done with Gmail the result is failed login so this is worth checking in your case.

An unknown is the age of this information and whether it has changed since this publication.

FWIW, if your goal is end up with a copy Pegasus Mail from an old machine to a new one then starting with a new installation of Pegasus Mail is not the easiest way to go.