It's difficult to help you, if you do not show us the exact values you are using.

Anyway, make sure the target path includes a file name (like /target/remote/path/file.ext).
Or if you need/want to use a directory path only, make sure the path ends with a slash (like /target/remote/path/).

I am able now to post the files on the remote server. Now we want to move them from their original spot to our archive folder. the following code
has in file, the folder path orig with the file, and the item.FolderPathArchive has the folder path of the archive folder.

It's not doing the move, am I missing anything here?

session.MoveFile(file, item.FolderPathArchive]);