If using a USB-cable or adapter between your cutting plotter and computer, you need to install a communication driver for it. Without the driver installed, your computer won't recognize your cutting plotter and it will not show up in the Output device / port list.
You can install the driver from the disk that came with your cutter. If you do not have the driver disk, you can download the driver from the company's website you purchased the cutter from or the manufacturers website.
If the driver is installed and the computer still does not recognize the cutter, there may be a hardware issue such as a bad USB port on the computer or cutter, bad motherboard on the cutter, or a bad USB cable.
If using another kind of communication method you can read more about it here.