I've tried 3 USB sticks so far and none of them worked

Here's what I found though, the P-Bus cable has one ends coloured BLUE, the other end is BLACK. I have the BLACK end hooked to the headunit, the BLUE end is connected to the OUT port of the CD-UB100. Is the cable directional?
After I read through the thread, I seem to have the cable connectors reversed. Can anyone confirm?
Thanks for your help.