What version and product of NoMachine software are you using on the Linux side?
What is the distro?
What’s the desktop environment?
Is it headless? See the tips here:
Connecting to Linux headless machines with NoMachine
https://knowledgebase.nomachine.com/AR03P00973
Is Wayland used?
Notes for connections to Linux physical desktops running Wayland
https://knowledgebase.nomachine.com/AR02P00969
Is it a virtual machine? If so, check this article:
Connecting to a Wayland-based desktop running in a Linux virtual machine
https://knowledgebase.nomachine.com/AR04R01083