I've seen that issue before. It means that our FTP service is working, but secure FTP connections are being blocked on your end.
There are three things you can do to resolve this:
- Configure FileZilla to connect with "Plain FTP" (not using TLS). This disables the security which is being blocked.
- Use a VPN to bypass the network filters so you can transfer files securely.
- Ask your internet provider or network administrator to remove this block so you can setup a secure FTP connection.