The 425 error means that the data channel is blocked or closed between you and the server you are trying to connect to.
For Active (PORT) connections open port 21. Also open inbound high ports above 1024 to the client. You can specify the range of ports the client uses for an Active data connection by clicking Tools, Options, Firewall, and check "Limit local port range". Open the matching port range you specify in your firewall.
For Passive (PASV) connections open port 21, and disable any outbound packet or command filtering.
If you still cannot get a successful connection, check all devices that are between the client and server to ensure that the proper ports are open (e.g. routers).
Another possible cause of the 425 error code is the SSL requirements on the server. In the case of the following error message:
- 425 unable to build data connection: Operation not permitted.
The server requires the FTP client to reuse the SSL session. In WS_FTP Pro (12.2 and later) to enable this option:
- Edit your site profile
- Click SSL on the left of the site options
- check "Reuse SSL Session" and click OK to save the change.