I have/had a similar issue with the VCI not activating correctly ( green light goes off after 3 seconds instead of giving three flashes then staying on), in my case it was the USB driver kept going back to "utms" (or something like, basically the default driver as the laptop comes with), whereas the install instructions showed how to get it to change to "multi instance". I'm afraid I forget exactly how one updates the USB driver to this multi instance mode, but the solution for me when I got it working seems to be to use the same port for the VCI every time. I taped off the other ports on my diagbox laptop so there's no chance of plugging into the wrong one.
Unsure whether that'd be any help to you, but it's been working for me on my eBay kit so hopefully it's similar.