Hi Jelisa57,
We appreciate you reaching out to us. We understand that you are getting a “The iCloud Apple ID is already in use by another user" message on your Apple TV.
We’d like to gather additional details that may help us be in a better position to assist you.
Are you receiving this messages on your other Apple TV?
How many user accounts do you have on the affected device? Set up multiple users on Apple TV - Apple Support
We ask because it is possible that you may have multiple user accounts on the affected Apple TV that are using the same Apple ID.
In the meantime, we recommend updating your Apple TV if you haven’t. While it isn't inherently assured that an update will resolve the issue, updating to the latest version of tvOS for your device can help isolate potential software issues.
Update your Apple TV
Take care!