Usually, orders are delivered instantly but may take up to 24h. When such delays occur, the purchase is still being processed and there's no need to try purchasing again.
If you have any issue with your order, it likely has to do with your billing and card information. To verify that your information is consistent, log into your mobile store or payment app and update it to match your payment method. Also, contact your bank to confirm any restrictions and details on your payment method and your mobile app provider