Please start here:
Why I cannot connect/transfer using script, when I can using GUI (or vice versa)?
If it does not help, please post session log files both from GUI and the script doing the same operation.

I am currently transferring some files from a local directory using WinSCP to a remote FTP server. I am able to do this transfer using the WinSCP Client application by drag and drop the files to the destination. I am trying to automate the process using winscp.com. However, when I try to do the transfer from local to destination, I am getting an error

Transfer channel can't be opened. Reason: The requested address is not valid in its context.

I tried to use both synchronize remote and put' commands to do the transfer. Both commands are returning the same error. I even tried to see if I can do a directory listing (ls) of the remote server from the script. This too gave the same error.

Please note that I am able to transfer file from the same local location using the client by drag and drop or by using the Synchronize tool from the client.

Could someone please help to identify the cause for the issue and suggest potential solution?