Hey Anonymous396,
If we understand correctly, you're trying to use the Sign in with Apple feature but are encountering an alert. We found the following requirements: How to use Sign in with Apple - Apple Support
"To use Sign in with Apple, you need to use two-factor authentication and be signed in to iCloud with that Apple ID on your Apple device. Learn more about Sign in with Apple."
If you do have two-factor authentication enabled and you're signed in with the correct Apple ID, we recommend reaching out to Apple Support to look into this more with you: Get Support
Thanks for using Apple Support Communities.
Take care!