To successfully implement the virtual USB bus, follow these general steps: Driver Preparation

A virtual USB bus is a software-based emulation of a physical USB bus. It allows multiple virtual USB devices to be connected to a computer, just like physical USB devices. The virtual USB bus is a software construct that mimics the behavior of a physical USB bus, enabling communication between virtual USB devices and the computer.

If you are having trouble with virtual bus emulators for educational purposes, Mastercam offers a free Learning Edition

Without these exclusions, the AV will quarantine the virtual bus driver mid-toolpath, causing Mastercam to crash with "HASP not found."

: Deleting and recreating the Windows User Profile has been reported to resolve persistent "Error 39" issues.

: Conflicts with other USB devices (like 3D mice) or corrupted registry entries can cause Mastercam to appear "running" in Task Manager but never actually open. Official Recommendations