Firefox - One Daily Site - Login Loops

[CraigS26]

This for another guy with a promise of a Nobel Prize and an appearance on TV's Jeopardy show for the answer.

On one website I use daily, I am -- unable to login with Firefox because doing so --- returns me to the login page --.

.....it works properly with all my other computers. I know it isn't my new computer because everything is normal if I access the site using Edge.
So the problem is either with Firefox or with some glitch between Firefox and my new Acer laptop

use CookieAutoDelete and have whitelisted the site.

tried using troubleshoot mode with the same result. I just stay on the login page, no error message.

clicked on the wrong thing in CookieAutoDelete and did not clear my cookies and cache. This time I did it right and I can now access the site. …. BUT Issue Returned

tried disabling all the items under Firefox's custom settings --- for privacy and security. No joy.

I tried disabling Privacy Badger for the site. No joy.

I told NoScript to allow all scripts, repeatedly until none were being blocked. No joy.
And as I said before, I tried troubleshoot mode to disable my add-ons.

Progress! I created a new profile, launched it in a new browser, and was able to log into the account.
.....It worked ONCE. I can no longer log in using the new profile. I don't think I changed anything

[StuartR]

Try disabling Firefox 'Enhanced tracking protection' for the site

[CraigS26]

Many Thanks, Stuart. Posted that and will Update when his Reply shows a result.

[CraigS26]

Stuart, it turned out that he found he could get in OK with MANUAL LOGINS BUT Failed with Saved Passwords via Autofill Logins & Passwords being checked. As I have prior (somehow), he's wound up with 2 Logins after thinking he Deleted the first and answering Yes when FF asked on the next attempt IF he wanted to save the Login data.

It's working Manually and the experts at Mozillazine FF sppt can keep at it if desired.
Many Thanks again. Got my OCD in a tither for awhile.

[StuartR]

Thanks for the update