There is a problem with MFA registration in Safari for both, hardware keys like Yubikey and TouchID. The registration succeeds but it's not possible to verify the MFA upon login.
If you registered a hardware key in Safari, use other browser to log in (it will work). Then remove the registered device and re-register it using the other browser.
If you registered TouchID in Safari, please contact support to have your MFA disabled to allow you to login. After that please reregister your TouchID the using different browser.