I purchased Business Plus, but I can't add another user.
Additional steps are below.
1.Click the "Add User" button in the "Add Managed User to Instance" block under "Accounts and Billing".
2.Click the "Add User" button and then click "Add User Manually".
3.Enter your “full name” and “email address”.
4.Click the "Save" button.
An error message appears saying "One user could not be added."
If you hover over the caution icon next to the email address of the user in error, a message will appear saying "User is registered with another company."
The user you are trying to add has already created a BOX account with the "Individual" plan.
The domain name of the email address of the user operating the operation and the user trying to add are the same.

What steps should I take to add it?