If a payment process has been canceled, then it can be completed during the next time the app is started. In this case you’ll receive the above message with the option to complete the process.
If you’ve received a receipt from the Google Play Store (receipts from the iTunes Store are sent out at the end of the month), please check if the Twists have been credited to your account balance (at the upper right corner of the screen). If you haven’t received such a confirmation mail, this usually means that the payment process has not been completed.
In the unlikely case of you having received a receipt but no Twists via the “Report an error” button in the settings and make sure to include the order number and the date of the receipt.