Could have been a faulty USB cable or port... too many variables to really tell you what caused it.
I'd suggest you start by connecting each deck directly, one at a time, to ensure that they are able to communicate with the computer - that eliminates the port, cable, and player as the problem. Next, add the hub into the equation, but still only connect each deck one at a time. If one CDJ doesn't appear, then the problem is the hub.
Re: Quantize, simply press the Quantize button to enable it.