Most purchase transactions (be they Gems in this game or other purchases in different apps) go smoothly. However, it might be possible that single transactions or requests from iTunes or the Google Play Store get delayed or result in errors. This might be one reason it can occasionally take a little while for your purchase to be delivered. If you experience such a delay, please wait for at least 24 hours.
In the meantime, don't attempt to make the same purchase again. As your previous order might still be processed, you will mostly likely end up getting charged multiple times. Please note that it is not possible for us to refund such additional purchases.
What you can do instead is to try restarting the game and see if Nonstop Knight 2 simply needed to refresh its connection to the server in order to deliver your purchased Gems.
If you still haven't received your Gems after 24 hours, please check your iTunes or Play Store Purchase History to see if your order was processed successfully.
Should you need further assistance with your order, you can send us your complete Apple or Google receipt for the order in question together with your in-game username. We will then look into your issue and help you getting your undelivered purchase.