Thank you! That solved my problem :)

I'd guess that N: is a network drive. Local policy can prevent applications running from network drives from accessing a network. Try running the portable version from a local drive.

See https://winscp.net/eng/docs/message_gethostbyname_unknown_error

martin wrote:

Either you have them configured differently

they are using the same .ini config file

martin wrote:

or the portable copy is blocked by Windows firewall or similar.

Can you attach log files from both?[/quote]
both the .exe file and .com are added to the to firewall exception for public and private networks. other than that I am at a loss

martin wrote:

Can you attach log files from both?

logs attached

The portable and installed versions are identical. Either you have them configured differently or the portable copy is blocked by Windows firewall or similar.
Can you attach log files from both?

I have only run the full version on the April 2018 Windows 10 machine,but it was successful

Where do you run the "full version of WinSCP"? On the April 2018 Windows 10 machine or on the other one?

Since running the April 2018 Windows 10 update WinSCP portable no longer connect to my FTP server.

It throws an error saying "gethostbyname: unknown error".

Running the same portable file from a PC that has not been updated works fine, as does running a full version of WinSCP using the same config file.