Most gem purchase transactions go smoothly. However, it might be possible that single deliveries or requests from Google Play, iTunes or the Windows Store get delayed or result in errors. This is why it can occasionally take a little while for your purchase to be delivered, so please be patient just a little longer wait at least 24 hours for your purchase to be delivered.
In the meanwhile, you should never try to carry out the same purchase again. As your previous order might still be processed, you will most likely end up getting charged multiple times. Please note that it is not possible for us to refund such additional purchases. Instead, you can try restarting the game and see if the server just needed a fresh connection in order to deliver your purchased gems.
If you still haven't received your gems after 24 hours, please contact the support with a copy of your purchase receipt.