mac app, SwiftyStoreKit.purchaseProduct, callback has never been executed

hi, i use the following code to purchase non consumable product for my mac app, at the beginning, everything is ok: i fill the test account and password, click confirmation buttons and so on, but after I confirm the last dialog, i wait and wait and wait, but nothing is happend, the callback has never been executed. i try again and again and again, but every time is the same. what should i do? did I do something wrong? thanks.

```
SwiftyStoreKit.purchaseProduct(productIdentifier) { (result) in
print(result) //the code here has never been executed
}
```
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Now i found that i should use a new test account to purchase the product, if the account has purchased the product already, the callback will not be executed. what should i do if i want the callback always be executed?