Connection Issues

Can anyone help, I already use FTP and am experiencing not connection issues at the same time that I am experiencing them with Smart FTP. I am trying to connect to FTP over a VPN which works file in FTP but not with the Smart FTP Client, here is a copy of the log:
 
2016-07-14T10:02:22Z Resolving host name "10.0.20.13"
2016-07-14T10:02:22Z Connecting to 10.0.20.13 Port: 21
2016-07-14T10:02:31Z Connected to 10.0.20.13.
2016-07-14T10:02:31Z 220 Microsoft FTP Service
2016-07-14T10:02:31Z USER websiteftp
2016-07-14T10:02:31Z 530 Valid hostname is expected.
2016-07-14T10:02:31Z Client closed the connection.
2016-07-14T10:02:31Z User authentication failed.
 
It looks like Smart FTP isn't resolving the IP address but Iour DNS is all correct and working with other clients. I was hopeing to give Smart FTP a proper Test as we need something a little more grown up.
 
Thanks
Colin