UPDATE 1/8/24: PROBLEM RESOLVED.

Any thoughts as to why the Opera browser (my default) all of a sudden is having problems logging into Delta? As of roughly Christmas, I had no issues, but now Delta does not recognize me. I enter my login info and Delta.com returns that it can't find my account. I do NOT have this problem on Edge, Chrome, the ipad, or the phone, nor on other computers, so the issue is unique to Opera on my PC. So it's clearly a setting of some kind. Opera is a Chrome clone, so anything that speaks Chrome is supposed to be able to speak Opera too.

I closed the browser, cleared the cache, cleared the history, nuked all cookies, rebooted the computer, made sure that cookies and popups are enabled for delta, disabled any VPNs, logged in on other browsers and affirmatively logged out, and still am getting a rock.

I remember having this problem once before, and to fix it required doing something amazingly, stupidly easy but not obvious. Any thoughts on how to fix it (besides "Well, don't use Opera and use _____ instead.")?