Without seeing the issue, it sounds like a user issue. Show us something. Just says that you failed the verification process. I'm able to access my icloud account. see screenshot

Uploading a screenshot of the error message. I have cleared the Firefox cache as well uninstalled and reinstalled Firefox to my laptop.

I have also attempted log ins using my fingerprint (passkey) and typing in my password. Both were unsuccessful. I am however able to log in via Chrome.

I resolved the issue by testing the login via a New Private Window. When it was successful I knew the issue was contained to the configuration on my laptop per Firefox. The solution was to clear not only "Temporary cache" but "Cookies and site data" as well. Did I lose some automatic logins? Sure. Did a few shopping carts get emptied? Absolutely. Small inconveniences.