If you see this error, for example when you use the ‘forgotten password’ link, it means that means you did not register a user account. Remember you don’t need to have registered to have added (nor to update) your business listing, so its possible you never registered (ie you made your contributions as an unregistered user). In this case just register (using the same email address) and the system will automatically assign your past contributions to your user profile.
If you’re sure you registered, did you click the link in the activation email (to activate your account)? Unless you clicked that link your account will not be activated.