thank you for reporting your issue to us. Information that “no desktop is available” is displaying on free license if server find running X server during startup but cannot find it when you connect to server using nomachine player. On our Lubuntu 16.04 NoMachine works well so may I ask you some questions which may help in investigation?
– If you run “sudo /usr/NX/bin/nxserver –status” command on server side, nxnode service is enabled?
– What is an output of command ps aux | grep X on server side?
– Do you start desktop environment in any non default way? Similar symptoms occures if you shutdown/startup display environment without restarting NoMachine server for example using init command.
– Do you use any non default Display Manager?
– Output of command sudo /usr/NX/bin/nxserver –version” from server side also would be helpful.
It’s very likely that running command “sudo /usr/NX/bin/nxserver –restart” on server machine will fix your issue. Anyway we will be very grateful for sending answers for questions above.