That's very peculiar that this should be happening, as it obviously sounds as though you have already established a connection. Have you tried running any example VIs? This is usually where I start to debug a problem. It shows me whether my code is wrong or something else (which is hopefully the issue).
I found a good example for you on NI's website which makes a call to both "Get File" and "Put File". It ran successfully for me. You may want to see if it gives you the same errors.
It's currently configured for an FTP server which I use, so you'll want to change its connection, but that's available through the front panel. Let me know how it works for you.
J.R. Allen