Transparent FTP connection returns 530-User Access Denied
Unable to connect to a remote FTP site
Packet captures show that the proxy is unable to connect to the remote FTP server.

Transparent FTP connection returns 530-User Access Denied when there is a network/server issue

If the proxy is unable to establish a TCP connection with the remote FTP server, the proxy will return "530-User Access Denied" to the FTP client. There is no FTP equivalent to the HTTP response code of '503 Service Unavailable'.

TROUBLESHOOTING:

For verification purposes obtain a packet capture from the ProxySG unit and examine it.  Check the connection between the ProxySG and the remote FTP server.  Make sure that the ProxySG is able to communicate with the remote FTP server.  If the proxy cannot reach the remote FTP server, then this confirms the communication or remote server problem.