Can you tell us what product you installed? Are you trying to start a session or start the server? When you lauch the application to start a connection, does it open? To check if the server is running, can you see the NoMachine Monitor icon (look for a !M) in the systems tray. For example, see Fig. 2 here: https://www.nomachine.com/how-to-disable-access-to-the-local-desktop.