Unable to connect via SFTP - (EFatal) Network error: Software caused connection abort

When attempting to connect via SFTP to host in the attached file, it is now showing an authentication error with this message (EFatal) Network error: Software caused connection abort. We are currently using version 5.15.2, which has not changed since the last time this connection was successful, which was yesterday. The login details have not changed.

Please see details in the attached log file.

Do you have any reason to believe that this is a WinSCP problem?
Can you connect with any other SFTP/SSH client?
Did you talk to the server administrator?