SerialPort.GetPortNames() does not list one of the comPorts in device manager

I'm trying to communicate with COM18 listed under Ports in my device manager without success. When I use the function call System.IO.Ports.SerialPort.GetPortNames() to see all the available ports, COM18 is not listed. Does this mean it's not a serial port? I'm trying to send commands to a power supply through USB interface.

Does the device manager listing disappear when you unplug the interface? Is the driver installed correctly?

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Originally Posted by Maylar

Does the device manager listing disappear when you unplug the interface? Is the driver installed correctly?

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Yes it disappears when I unplug the interface. The driver that I got from manufacture site is installed correctly I think. It shows up under Ports in device manager.

Plug the device in. Restart the PC. After the restart check the device manager and try with the name listed.