Does cis-broadband even offer IMAP/POP3 and SMTP email services? Maybe they do, but I can only find references to their web mail service. The web link you show above looks like a web mail address that wouldn't be valid for IMAP/POP3/SMTP. Also, the link doesn't work, at least at this moment.

It's a pop & smtp server, I lost access to the online web mail, and was trying to get to the server over the broadband direst connection, I had it working for years but seldom used it. Now I can't get it to connect again.

What are the POP and SMTP server settings, as far as you know?

I just noticed that the URL you mentioned above is incorrect - there should be two slashes, not one. Corrected, it takes me to a log in screen, but with a security warning.

I find it odd that none of their web pages are encrypted/secure. Even with a https prefix, the email address from above is reported to be insecure. They look like a pretty small operation.

They are a small provider, but the only other options are satellite or old copper DSL, that was error ridden. do I need to enter the whole address, HTTPS://mail.cis-broadband? I think when I upgraded Thunderbird, is when the problem started, and I changed so many things in settings, I really broke it.

That would be the address for webmail only. The "https://" prefix isn't appropriate for SMTP and POP servers - you indicate the security in other settings.

Try simply "mail.cis-broadband" for both and see where that gets you.