Google recently announced that Brand Accounts are no longer supported for G Suite for Education school domains. They will be revoking membership of user accounts from Brand Accounts on July 10, 2019.
Google suggests looking into your Brand Accounts at https://myaccount.
To preserve any existing content associated with a Brand Account, Google suggests downloading your data while logged into the Brand Account.
Our SEO team suggests transferring primary ownership of the Brand Account to a non-G Suite for Education Gmail account using the following procedure: https://support.google.com/accounts/answer/7311601.
Although Finalsite Support cannot help with the transfer of the account, we hope that these articles from Google will help you with the transition.