I've read that you need to move the pad ever so slowly. once trained in an area, they know that area to use. I've witnessed this first hand.
But, it's not their fault. I've also done the moving of the pad slowly and it's work too.
Look at it this way, they've learned and they are pottying where you wanted them to so that means they've learned something! Good luck and remember, they learn what we teach them.