Older Apple TV

What model of Apple TV exactly? If its a 2nd or 3rd generation, make sure its software is updated. If its still running older tv firmware, access to the iTunes platform is restricted.

See here: If you can't access the App Store or other Apple media services, or can't edit your payment information - Apple Support

and here: Identify your Apple TV model - Apple Support

and here: How to update your Apple TV - Apple Support

Hello,

This sounds like it is related to Two-Factor Authentication. You will need to generate a secure code and type it after your password. Example: password123456

Two-Factor Authentication