Windows 10/11's Driver Signature Enforcement. Solution: Restart Windows, press F8 on boot, select "Disable Driver Signature Enforcement," then install the driver. Alternatively, update to the latest official driver (post-2020 versions are signed).
provide compatibility for newer Windows versions (Windows 10/11) and Mac. Connectivity & Installation Tips Mutoh Sc 650 Drivers Download
Software for Mutoh SC-650 plotter (download manual - PlotCalc Windows 10/11's Driver Signature Enforcement