If you see an exclamation mark in under "Universal Serial Bus Controllers" or "Other Devices":

Troubleshooting issues with your Mastercam virtual USB multikey not working can be a challenging and time-consuming process. However, by following the steps outlined in this article, you can identify and resolve the issue, ensuring that your Mastercam software is running smoothly and efficiently. Remember to keep your software up-to-date, monitor your license, and maintain a stable computer configuration to prevent future issues. If you see an exclamation mark in under

If the drivers seem fine but Mastercam still won't open, use the built-in licensing utility.

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. If the drivers seem fine but Mastercam still

Windows 10 and 11 require all drivers to be digitally signed by Microsoft. Since MultiKey is often unsigned, you must manually bypass this: Hold and select Restart from the Power menu.

💡 Most failures are caused by Windows Security updates revoking permissions for unsigned virtual drivers. If you'd like to dive deeper, let me know: Which version of Mastercam are you using? What Windows version is on your machine? What is the exact error message displayed?