Hi elan,
unfortunately the logs you sent are not complete and not useful for the investigation. Please send a complete set of logs as explained in details here: https://www.nomachine.com/AR07K00677. If you wish, you can send them to forum[at]nomachine[dot]com by referencing this topic in the subject.
But before that, can you tell something more? I see you are connecting to a Xvfb display. Is this a headless machine and you followed instructions in https://www.nomachine.com/AR10K00710? Have you launched a desktop environment (or any X application) inside the Xvfb display?