What version of WinSCP and WinSCP .NET assembly are you using?
My guess is that you are using the latest RC version of .NET assembly, but old version of WinSCP.

If this does not help, please attach a debug log of WinSCP .NET assembly (set Session.DebugLogPath).

Hello
I try to use WinSCP.dll in ps script on 2008r2 server
and see this error:
Exception: WinSCP.SessionLocalException: Element "cwd" not found in the log file
at WinSCP.CustomLogReader.WaitForNonEmptyElement(String localName, LogReadFlags flags)
at WinSCP.CustomLogReader.WaitForNonEmptyElementAndCreateLogReader(String localName, LogReadFlags flags)
at WinSCP.Session.Open(SessionOptions sessionOptions)

by the way i use 5.6 rc dll version where exist SshPrivateKeyPassphrase option

please help me