This happens to me all the time since the store change-over: I log in, add an item to my cart, the page refreshes, and when it comes back up, shows that I have 0 items in my cart. If I try to add the item again, it tells me that I can’t add more than 1 copy of an item to the cart. The most reliable “fix” I’ve found for this is to log out and then log back in, and when you check your cart, you should see the item. DAZ is either unaware of this, or it’s not important enough for them to correct it.