Are you able to FTP to the same server using any other FTP client?
I have no clue, I wouldn't know how to do that. I am not tech savy at all. How do you do that?
Launch any browser and enter ftp://www.YOURSITE.com/ . It will promt you for authentication.
Enter the FTP username and password. Verify whether it goes smooth.
Otherwise download any FTP client like, FileZilla and try to connect using it.