Forum zgromaźeństwa Firefox

We tried 2 different computers, but two different users. Type in the user name and the password and it looks like it will start up, but then returns to the login paged.

This is the link to the video that will not play in FireFox. https://www.swingtechnologies.com/UploadVideos/clarkj@pobox.com/S200629_019 B.mp4

So I understand this: https://support.mozilla.org/en-US/kb/xframe-neterror-page and the reason it exists, but I need to find a way to turn it off because it's literally blocking me from accessing the Library of Congress webpage inside the same browser for my job. It's not a malicious site, but I can't figure out how to tell Firefox to stop blocking it as if it was a malicious site.

Help.

In Firefox, and only in Firefox, I get 'Failed to verify your identity' on these sites. I have updated MacOS and Firefox, rebooted, tried a different DNS, and disabled all of my extensions. With extensions disabled I don't get the error, but the login site won't accept my login at all. See the attached image. I can't think of anything else to try.