I tried version 6.12.3, and version 7.7.4 and both work as expected and without issues on Windows 11. This looks as the installation problem happened on specific environment.
Please can you try uninstalling NoMachine and reboot host and report if here are any uninstallation errors. After reboot verify if NoMachine folder still exists “C:\Program Files (x86)\NoMachine”.
If exists rename it and then install NoMachine again. Important is to reboot Windows after installing NoMachine to correctly load needed drivers.
If you still experience the problem, after new install, collect NoMachine logs ( DT11R00181 – Collect server and client logs manually ) and attach it to this post, or send to forum[at]nomachine[dot]com.