Unable to log into Comcast Business Portal to Pay Bill

For the last year, I've been using a Linux Mint workstation to log in and pay my Comcast bills at https://business.comcast.com/myaccount or at https://login.xfinity.com/login?r=commercial&s=oauth&continue=https%3A%2F%2Foauth.xfinity.com%2Foauth%2Fauthorize%3Fclient_id%3Dcomcast-business-myaccount-prod%26redirect_uri%3Dhttps%253A%252F%252Fbusiness.comcast.com%252Fmyaccount%252Fsignin-cima%26state%<redacted> without issue.

Today, my Linux system Firefox 91 tells me it cannot connect to oath.xfinity.com -- but I fired up a less secure Windows workstation and was able to log into the portal just fine.

What is Comcast web dev team doing that impacts my Linux workstation?  Please let them know that they're creating a negative experience.  Me, I'm ditching Windows, don't like Mac, and trust my secure Linux workstation far more than the other two.  I use FireFox with a bunch of addons, like Privacy Badger, AdBlock Plus, NoScript, EFF's HTTP Everywhere, and DuckDuckGo Privacy Essentials.  I even fired up a profile on the Linux FireFox that did not have NoScript loaded.

We don't need a return to the bad old days of "This is a Windows Explorer only site" or "This is a Netscape only site."  And you guys shouldn't be playing cross site scripting games as those tend to be insecure.

I tried to find a place to post this that seemed more appropriate, but Business Internet was the best I could find.  Website feedback seems to be lacking anywhere I looked.  And yes, I am a business class customer.