We're sorry for the trouble. This can sometimes happen due to a temporary issue with Apple's servers.
Please restart your iPhone and open the app again. If it still doesn't take effect, tap "Restore" on the Premium Pack screen. You won't be charged twice as long as you use the same Apple Account, so please rest assured. If it still doesn't work, please contact us using the "Contact Us" button at the top right.
We apologize for the inconvenience.