Make sure the path of the remote file is not in Windows format, i.e. it should not have a drive specification (e.g. "C:") and it should use forward-slashes (i.e. "/") instead of back-slashes (i.e. "\"). Also, paths are usually given with respect to the "home directory" of the FTP account on the server. This is different from the absolute path on the server.
For example, if home directory of a user account on a Windows-based FTP server is "C:\myftpserver\home\myusername" and the file you want is "C:\myftpserver\home\myusername\mydir\myfile.dat", then the path that you should use would be "mydir/myfile.dat".
You might find it helpful to use a GUI FTP client like FileZilla to familiarize yourself with how file paths are specified in FTP.
- Hans (EDT)