title: SKStoreProductViewController().loadProduct() does not work in iPad
body: <p>Since 2 days I've a got this problem.
  In my app I want to display the SKStoreProductViewController() for my cross promotion. In my Iphone 7 the loadProduct() function reach the completion block but in my iPad it never reach it. So I'm not able to dispay the StoreProductView on my iPad.
  I try to set the identifier as Int and as String, but it's the same problem. No one works.
  In both device I have the same itunes account connected.</p>
  
  <p>I don't know where is the problem.</p>