Once you have the driver working, keep it that way.
If you work in a school or shared workspace where you cannot install drivers, use this workaround. redsail cutting plotter usb driver install
This will not install a permanent COM port, but it will allow your cutting software to talk via raw USB. Note: This is a last resort; COM port stability is superior. Once you have the driver working, keep it that way
Once the driver is successfully installed, you must identify the virtual COM port number assigned to your plotter. This is the "address" the software uses to talk to the machine. This will not install a permanent COM port,
If you own a RedSail RS720C or RS1350C, these plotters have a unique motherboard that requires a vendor-specific driver wrapper. The generic CH340 driver will show a successful install, but the plotter will not respond.