This is not a recognized issue by Apple as far as I can tell. A preponderance of user reports say the solution is to use a browser other than Safari.
Related discussions:
https://discussions.apple.com/thread/255037783
- "Someone in another post said to use a different browser (not Safari or whichever one you normally use). That worked for me."
- "Use a computer to generate the App specific passwords. Don't use Safari or Chrome. I got it to work using Firefox on my Mac."
- "the Chrome browser works for me."
Can't change Apple ID - Apple Community
- "OK it just worked. No idea what was going on before. Thanks for the help anyway!"
Can't Change / Remove Apple ID Notificati… - Apple Community
- Occurred while changing account information using a web browser.
https://discussions.apple.com/thread/255040675
- "The solution to the problem is not to allow the iPhone or Mac to sign you in automatically with FaceID or TouchID, but instead I found complete success in manually signing in with my Apple ID and password, which then prompted a two-factor authentication prompt and code. Following that sequence, I was able to successfully revoke and add app-specific passwords."
I'm trying to add a new app-specific pass… - Apple Community