Why is WinSCP not able to connect to a server, when other clients are?

If you are getting an error message like “Connection refused”, “Connection timed out” or “Can’t resolve host name”, it is likely that there is a local firewall set up with per-application rules. The rules may allow the other clients, but not WinSCP.

You may also start getting the error after upgrading WinSCP. Some firewalls check executable file fingerprint. As the executable file changes with upgrade, the firewall starts blocking the executable, although you may have added exception rule for WinSCP already.

For built-in Windows firewall, go to Control Panel > System and Security > Windows Defender Firewall > Allow an app or feature through Windows Defender Firewall.1 There you can add an exception for winscp.exe.

Note that some antivirus software have some firewall functionality built in. So check even your antivirus settings (or try to turn it off temporarily for a test).

For other reasons of getting refused to connect, please read documentation.