I have the exact same hardware/software version, with the same issue.
The software is in the last version available.
Yesterday I got a problem with Netflix authentication (basic things already checked, username, password, etc). According to Netflix, I should try typing the username and password directly from the remote control. I did it and did not work.
After that, I followed the next Netflix recommendation and reset the hardware. At this point, neither Netflix nor ICloud was able to authenticate. For iCloud, I tried with the wrong password and correctly got the wrong username/password error. Using the correct username and password, I was asked for the 6-digit two-factor authentication number. Typing at the remote control after the password authentication or including it at the end of the password as suggested, I got the same error.
I also tied the same process using restore rather than reset but got the same error.
Any hints?