Hi RHELuser,
Currently Gnome 3 (default desktop in RHEL7) doesn’t work in virtual sessions.
A workaround is provided in the article “Supporting the default Gnome 3 on Fedora 15 or later with NoMachine” (https://www.nomachine.com/AR06L00806)
NoMachine 5.0 will enable Gnome 3 and Unity in virtual sessions.