I have recently had an issue connect via Winscp to a Vcenter Appliance.

When SSHing to the same server run the following command:  chsh -s /bin/bash root

The following message was displayed.

You are required to change your password immediately (root enforced)
chsh: PAM: Authentication token is no longer valid; new one required

To fix reset the password using the passwd command (you can use the same password as before as it does not check if it is different).

Then Winscp connected as expected.