I have a curious issue here. I am using a Raspberry Pi3 and the arm7hf version of NoMachine. The installation on both the server (my pi3) and client (mac osx high sierra) works fine and I am able to connect successfully on the Pi.
The problem is that using the KANO OS (Educational OS for children and schools worldwide, more at http://www.kano.me), I am unable to get the Dashboard screen transmitted. Instead, I get only the Desktop background with the clouds.
The OS is based on Raspbian Jessie but the Dashboard is built using Qt5.7. It’s an Open Source OS (Github on KanoComputing) and the newest image is in http://dev.kano.me/public/4G/img/en_US/Kanux-Beta-v3.14.1-Lovelace-jessie-release.img.gz.
We dumped the X.org framebuffer with xwd (https://en.wikipedia.org/wiki/Xwd) and Dashboard screen is also corrupted there. So the problem is on Xorg side, not NoMachine. We suggest you use “Classic Mode” during NoMachine connections.