Any specific error messages from the ECMLink app?
The first thing to make sure is that the V3 cable is being recognized by the laptop as an appropriate adapter.
Plug in your cable and check your COM ports in the device manager to see if it is being recognized properly. After the ECMlink application finds the cable, the rest should take care of itself. Proper configuration should solve your problem, but you can only configure a device if the computer sees it, recognizes it, and assigns it a port.
If the cable itself is not being recognized as a device, then it's probably bad... Thomas Dorris from ECMTuning was guiding me through a similar situation just the other day - new cables are $39
Try reinstalling drivers and make sure the cable is being recognized by the actual laptop first.