There was a problem connecting the "data" connection to the server, it has not responded.
You can try within FTP On The Go: on the "Settings" tab, in the "Security" section, to switch off the top two items.
If that does not help, you may need to add some "Port Forwarding" settings on your router.
The replies from the FTP Server indicate that it is behind a router or firewall and the router isn't recognizing the FTP communications to open and forward the correct port for the "data" connection. This most often happens for a FTP Server running on your home network, especially with the security settings turned on or if you are using a non-default "port" for the main FTP Server (ie, not port 21).
You very likely need to add some "Port Forwarding" settings on your router.