The best questions are the ones you can answer yourself.
For the benefit of others that may be searching the forum in the future; the user-name you use to log-in via FTP or the Shell is any of the valid usernames you have configured in the panel. You can list the valid users by going to Users -> Manage Users in the panel.
Note: If you intend to upload files for a particular domain, you must log-in using the user that controls that domain.
Note2: You need to enable Shell access for a particular user to log-in via SSH.
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