I created a new Apple ID and tried to use it in the same Macbook Pro 2016 as the old account. I've logged out and tried to log in with new credentials, after that I've seen an alert with terms to accept (I accepted it), then just "ACCOUNT_UNAVAILABLE" alert without any details. What does it mean?
Also, tried to update Macbook to the newest version (currently - 11.6 Big Sur), but without any change.
How can I fix it?