In the subject of the report, you refer to FTP, but SSH is visible in the log (or SFTP if it is an SFTP connection). The FTP account created in the panel is an FTP account, not an SFTP account. The credentials for SFTP and SSH are the same as for the hosting account panel. Failed logins result in IP blocking, and the unblocking form is linked in the contact section on our website.
https://www.serv00.com/ip_unban/
The message "SSH Error: failed to negotiate key exchange algorithm" suggests that you may be using an outdated SFTP/SSH client.