You have attempted to log in to Model Insider with an account that is not yet activated. When you registered, an email was sent to you with a link to activate your account. If you did not get this email, there's a chance that you either gave an incorrect email address or this activation mail is sitting in a spam filter. Please ensure that you are enabled to receive email from addresses @modelinsider.com and that no spam filtering is taking place on email from that domain.
The activation email has been automatically re-sent to you, and will be re-sent every time you attempt to log in prior to activating.