Itunes not detect apple tv 3 dfu mode

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 passed the time limit.

The restore procedure through a computer is intended to install the the current software 7.7 (not downgrade) for that model.

Restore your Apple TV - Apple Support

- Be sure to use a USB cable that supports data transfer. Charging cables from other devices may not support data transfer.

- Be sure to power the Apple TV (3rd generation) at the indicated moment.

Two-factor authentication is an account property, not a device property. That wouldn’t change with a different software version.