Failed to verify your identity error for Apple ID or iCloud

I had to create a secondary AppleId just to discuss this problem. I need to get to the website

https://appleid.apple.com/account/manage. Even though I normally browse on Windows 10, the error occurs everywhere. From my IPAD, after typing AppleId and Password, SAFARI reports "Failed to verify your identity. Try again." Apple does send the 6-digit two-step verification code to the same IPAD, but SAFARI does not prompt for the code. It only gives the error and stops me. Same error using Firefox on IPAD. More importantly, same error while using Firefox, Edge, or Internet Explorer on Windows 10.

[Re-Titled by Moderator]