Maybe you used your Broker member area login data. When you create your Account with your Broker, you get a Member-Login and an MT4 Account-Login. The Member login is your e-mail address and a password. This should be used to enter the Broker Webpage. After creating your MT4 account, you have received a confirmation email. In this email, you will find your login details. For the MT4 login you need your account ID (Trading number), the server name, and the password.