title: paymentQueueRestoreCompletedTransactionsFinished: is returning an empty queue when it should have transactions in it
body: <p>This is my first time using Store Kit and everything has gone great up until I attempt to restore purchases. I've seen several other posts on stack overflow about similar issues but I've not found a solution that works for me.</p>
  
  <p>I have a button in my app that calls <code>[[SKPaymentQueue defaultQueue] restoreCompletedTransactions]</code>. This in turn triggers the <code>SKPaymentTransactionObserver</code> method <code>paymentQueueRestoreCompletedTransactionsFinished:</code>. The problem is that <code>paymentQueueRestoreCompletedTransactionsFinished:</code> has zero transactions in the returned queue. </p>
  
  <p>If I then attempt to make the purchase I am notified that I have already made the purchase. This tells me that the store knows that my test Apple ID has successfully made the purchase on a previous attempt. Why then does <code>paymentQueueRestoreCompletedTransactionsFinished:</code> return an empty transactions collection on it's queue?</p>
  
  <p>There has been some mention of the sandbox behaving erratically but I need to see this working before I go live to the AppStore.</p>
  
  <p>Any ideas? Am I missing something?</p>
  
  <p>Thanks in advance.</p>