Because I have AR, and can clone on White, but I can't find a clone code that works for US Black version.
On my White, I have a code where you just press Select anytime, and the clone will always be active.
On my Black, I have found what are basically the same clone codes, but with different activator buttons.
I am told to hold down the activator button while moving the Pokemon. I do this (with all three codes), but it never works.