Even though all other remote control options (console, SSH, VNC) succeed, when you try and establish a connection to a VM using secure RDP, it fails right away. All required ports are confirmed to be open and direct RDP connections are also successful.
This occurs when the target VM is configured to accept only connections that use Network Level Authentication (NLA), which requires authentication be completed before the remote desktop session is established. At this time, the only options are to configure the target machines to accept unauthenticated connections (users will still be challenged for credentials) or to use one of the alternative means offered by vCommander to connect.
Please contact firstname.lastname@example.org if your organization enforces Network Level Authentication. We are currently tracking affected customers with an enhancement request.