In some cases it has been noticed that an USB device forwarded to Linux servers works fine but only at the begin.
If the NoMachine session stays running for more than 2 hours, such device might get disconnected. 

When this happens, the output of the 'lsusb' command no longer shows that USB device on the server host, and the 
NoMachine player shows that the device is still connected (green dot).

As a workaround, disconnect and reconnect the USB device.