Since version 6.1.6, NoMachine USB drivers are automatically disabled on Windows systems to avoid conflicts with the drivers listed below.
To be able to use NoMachine USB forwarding module is necessary to uninstall such drivers and use the default Windows USB drivers.

Conflict between ASMedia USB Controller drivers and NoMachine USB driver (nxusb) leading to BSOD occurs on Windows laptops. 

This problem occurs when the laptop is running docked. In particular, it has been reported with:

Dell Precision 5510 with Thunderbolt Dock (TB16) and ASMedia USB driver v. 3.1.

In NoMachine since version 6.1.6 if this conflict appears the USB devices panel will be grayed out (no local nor remote devices will be shown). The followig line of log could be found in the file nxdeviced.log:

CheckAndUpdateServices: WARNING: Conflicting driver has been detected in the system. USB service has to be disabled.

A way to check if you have ASMedia USB Controller drivers installed is checking if the following file exists: 

C:\WINDOWS\system32\drivers\asmthub3.sys

Possible solutions:

(i) Update ASMedia USB Controller drivers.

(ii) If possible, use default Windows drivers instead of ASMedia drivers. Uninstall ASMedia USB Controller drivers from the system and Windows will automatically use instead of them the default USB drivers provided by Microsoft. After uninstalling the driver and restarting the host machine, double-check that the driver file C:\WINDOWS\system32\drivers\asmthub3.sys is deleted. 

(iii) For NoMachine versions previous than version 6.1.6: manually disable NoMachine USB drivers (if it's a NoMachine server installation, e.g. NoMachine free) or uninstall them. Instructions to disable or uninstall drivers are available here: https://www.nomachine.com/AR12O00955.