Window Server Error

Hello, WinSCP support,

Recently, We changed our Windows Server 2016 to 2019 to use WinSCP.
But we have had a problem that we have been attempting to install WinSCP on Windows Server 2019.
Error message appeared as attachment that I posted.
We also checked service running of OpenSSH that we completely installed.
Additionally, PuTTY is operating as well.
It would be appreciated if someone could help with this issue.
Thank you.

PuTTY is an SSH terminal client. It's not an SFTP client. The SFTP seems to be broken on your SSH server. Verify with any other SFTP client (e.g. PuTTY psftp). They will likely fail too. Check your SSH server log. You might have Subsystem directive in sshd_config file misconfigured.