How to remove apple TV from MDM when already released from Business Manager
I was reading this post, but managed to figure it out when Apple Support couldn't.
How to remove AppleTV 4K from Remote Mana… - Apple Community
The solution was simple. Press and hold down the back and home buttons on the apple remote until the Apple TV says it is having an issue, and gives you the option to reinstall. Do so, and your problem is solved.