Hi there,
Welcome to Box Community and glad to assist!
Let me create a new case and a member of our team will be in touch, please keep an eye out.
Thanks for posting!
I too have received the same error message when trying to add a user.
Was this resolved? I am having the same issue.
I am having the same issue. The person I am trying to add had a personal Box account with that email address, but he deleted the personal account. I still cannot add him and it says his email is already associated with a personal Box account.