I have an AppleTV 3rd generation (A1469) that will not login to iCloud. After entering the correct password I get
"Unable to sign in. Could not communicate with server".
If I try the wrong password, it gives a different error saying wrong password. My account has 2FA enabled. I've read unofficial forum posts saying you need to use a "decorated password" which is your password plus the 6 digit 2FA code appended. But in this case my iPhone does not show any notification about a login attempt. I've already tried "Reset all settings" in the menu and it's running the latest OS 7.3. Network test does not identify any problems.
Best Answer
It turns out this is what happens when you have 2FA enabled. The solution is to get a verification code from an iOS device. Then use this 6-digit code together with your password on the AppleTV. So if my password is
mypasswordthen I would enter likemypassword123456.Settings > Apple ID > Password & Security > Get Verification Code