I think I just discovered a serious bug.
Steps to reproduce:
- Change iCloud password on your iPhone
- Sign out of all devices after the password change
- Try signing into other Apple devices using the new password
- Unable to sign into my iCloud account on my iPad Air, ATV 4K, 14" MBP despite repeated attempts.
I'd been trying to log into my devices and the password verification always fails despite entering the correct password and the 2FA code. All my devices run the betas of latest OS.
EDIT: Took me 2 hours but finally got the devices signed in.