IntellaSphere uses emails as the login and primary identifier for each account. So, if a user already has an account (or, gasp, is cheating on you with somebody else’s IntellaSphere account), they cannot connect to a new account.
In this case, you can either sign up with a different email address or ask them to have the other account Admin remove them. If you have an old account that you don’t need anymore, you can reach us by email anytime at Support@IntellaSphere.com, and we can deactivate it for you to free up the email address as well.