More information about "Transfer channel can't be opened" error:
https://winscp.net/eng/docs/message_transfer_channel_cant_be_opened

martin wrote:

Since 4.3, the passive more is default for FTP. Maybe you need to use active mode.

Thank you, took me a while to find the option, but now it is back to working on the new one. Thank you for your time :).

Since 4.3, the passive more is default for FTP. Maybe you need to use active mode.

Was using 4.2.8 upgraded to 4.3.2 and started receiving an error when connecting to my Western Digital My Share Space (4tb raid 5 NAS).
Error message text below
*******
Transfer channel can't be opened. Reason: No connection could be made because the target machine actively refused it.
Could not retrieve directory listing
Entering Passive Mode (70,240,176,161,19,142)
*******
followed by timeout detected, and if/when it does come up, no directories exist. The only thing I do to receive this error is double click the User@IP address in my saved list. Tried updating my NAS same problem. It works again after I uninstall the newer version and reinstall the older version (still have the install executable) and still has the problem after "full Upgrade" back to the new one.
Windows 7 x64 SP1 Professional
FTP (no encryption)
Commander
My NAS system version:
*******
Description NAS Firmware
Version 2.2.91 with MioNet 4.3.1.12
Last Upgrade Fri, 25 Mar 2011 00:50:40
*******

edit,
as a note to the programmer/programmers, thank you very much this is and has been the best I have seen for ftp software for a long time, and your price can't be beaten :)