Email already used in a Box account but not associated with an enterprise

I am getting the "Email already used in a Box account but not associated with an enterprise" error message when try to add managed user. After several attempts on my part to add the user, I had him delete the account - it had no files associated with it. I used to get the additional message or 'Groups and Folders selection, as well as User Settings for existing Box users, will be available after the user(s) accept their invite."  I read, in some support thread, about clicking the Save a second time, so tried that, but the error messages didn't seem to change and the user didn't receive an invitation. Now when I try to add user again, a message flashes up that says "You do not have permission to add users. Contact support" or something like that.