This error message indicates that the authentication process between your local computer and the remote host computer has failed.
The most common cause for failed authentication is an incorrect password, likely caused by a typing mistake.
The user name may be incorrect. Check that you have typed it correctly.
One possible reason for authentication failure is that the remote host computer may have been configured to require several authentication methods to be used. For example both password and public-key authentication could be used for increased security. Even if you entered your password correctly, another required authentication method could have failed. A relatively common situation is one where the remote host computer is expecting public-key authentication and you have not sent your public key to the host. You can do this by following the instructions in Section Uploading Your Public Key.
It is also possible that your account on the remote host computer has been disabled, or that the remote host computer is having temporary problems that cause errors with the login procedure.
Try to connect again and carefully type in your user name and password. If after a couple of retries you are sure that you have entered both of them correctly, contact the system administrator of the remote host computer.