You must make sure to install the USB drivers.
I have found that connecting the USB driver is not always a perfect solution. The computer can become clogged with alocating serial port numbers so high that the software doesn't recognize the USB port number. Try a different computer.

Make sure the USB cable is good.
Make sure the electrical source does not have distortion from welder, powder coating system, or otherwise... I use a TripLite LC-1800 power line conditioner.

If the USB cable fails and USB disk fails... it might indicate that the power supply is failing.. or the controller is going bad.

Thank You,
Ray Scott