Is it normal that purchaseProduct() sometimes doesn't open anything for minutes and somethings works within seconds?

*Sandbox Environment*

***

I've been testing auto renewable subscriptions and sometimes nothing happens when I click my purchase button, there is no purchase UI coming up.

```swift
print("subscribe pressed")
SwiftyStoreKit.purchaseProduct(IAPSingleton.s.subscriptionProductID, atomically: true) { result in
print("result") // This also doesn't appear
}
```

Is this to be expected during sandbox/ when the account has already made a few purchases or is this a library issue?