That line means Windows does not know about the user that our plugin gives it. Probably because it is passing "Default\gemechis", and there is no domain or workstation called "Default" in your Windows installation. You have to figure out a way to tell the plugin the specific domain you want: "COOPBANK\gemechis", etc.
In older versions of our plugin, it had a bug where it would try the domain "Default" by default, and you had to be explicit about the domain when logging in. If you're stuck with an older version, that's your workaround. Otherwise, use the latest version of our Windows plugin.