NoMachine doesn’t currently support the Wayland X server (though we are working on adding it) and Fedora 23 uses this X server as default. You can temporarily switch to lightdm which will use Xorg instead.
Steps to change display manager from gdm to lightdm are as follows:
[root@test01 ~]# dnf install lightdm
[root@test01 ~]# systemctl disable gdm
[root@test01 ~]# systemctl enable lightdm
Reboot to make changes effective:
[root@test01 ~]# reboot