Windows will detect the CP2102 if things are working. Do you get a red light on the CP2102 when you plug in the USB cable? The CP2102 is powered only from the USB port of the computer, so if you don't have a red led, you don't have a good connection to the computer. Perhaps your cable is bad?
If you have a red led but no COM port in the device manager, then perhaps your USB cable is a charging cable, not a data cable. Again, try another good USB cable.
The CP2102 will light red and show as a COM port without power to the OnStep controller. Another possibility is the CP2102 is defective.
-Mike