Are you sure your target path should be in Windows-style (starting with
"C:" )? Most of SFTP servers use an unix-like virtual filesystem without drive letters. If your SFTP server has a physical root directory
"C:\Sftp_Root", then the virtual path should be
"/" and your upload command should be:
If your SFTP server really accepts (and needs) a physical path like
"C:\Sftp_Root", please connect to that server with another SFTP client software (e.g. Filezilla) and send us a communication log from that software.