Perhaps you didn't make a very good list or you may have chose a very competitive shop, there's lots of reasons why you might not have bought anything. And when you give a manual list it doesn't need the profit margin, that's only for people using the database lists. If you provide your own list it will only purchase items which are in your list.
But if there isnt a profit margin, then its going to buy the items on your list at highest price leaving no room for profit. Do you know a really good item that is well searched in Shop Wizard? Im trying to find the niche