On Windows 10 and 11, a security feature called "Memory Integrity" (Core Isolation) can block virtual drivers from loading. This is a very common cause for this specific error.
If you are running advanced virtualization software (like Docker, Hyper-V, or VMWare), these can lock the USB ports in a way that prevents the Virtual Multikey from attaching. mastercam virtual usb multikey not working
Before fixing the problem, you must understand what you are dealing with. On Windows 10 and 11, a security feature
The Virtual USB Multikey is a kernel-mode driver (typically mulfox.sys, multikey.sys, or vusbbus.sys) that creates a virtual USB controller in Windows Device Manager. Mastercam's licensing service looks for a physical HASP (Sentinel HL) on the USB ports; the virtual driver tricks the software into thinking a real dongle is plugged in. If you are running advanced virtualization software (like