the logs excerpt are from version 3.5.0 client. NX 3.5.0 is now dealt with via the traditional support channels, so I suggest you use the contact us link at the bottom of the website if you need further information about backward compatibility between versions. That said, the logs show that you are trying to connect using SSH (port 22), and SSH is not supported in the free NoMachine server. Try installing the NoMachine 4 client on Windows and report back. By default it uses port 4000 (NX protocol). If you want to continue using port 22, you need to install the Workstation on the remote server host.