My Apple TV box won't accept my Appleid

On Apple TV (2nd or 3rd generation), you can sign in for the iTunes Store, but you cannot sign in for iCloud services anymore. iCloud has changed, but the legacy Apple TV system software has not changed with it.

The service ‘My Photo Stream’ has been discontinued for all users, all devices, and all software versions.

Also see: Apple TV box iCloud login issue, how to solve - Apple Community

It is the iTunes Store on the validation set up that I am using.

If you have an Apple TV (2nd or 3rd generation) and two-factor authentication for your Apple ID, then you may be asked to type your password followed by the six-digit verification code directly into the password field. Additionally, there is a time limit, after which the code becomes invalid.

Try this: First enter the characters of your password (do not submit yet), then manually request a new verification code, then append that code to the password (no spaces or other separating characters), and then submit. That should help you get past the time limit.