We apologize. This can sometimes happen due to a temporary issue with Google's billing servers.
Restart your device and open the app again. If there's still no effect, tap "Restore (Purchased in the past)" on the Premium Pack screen. As long as you use the same Google account, you won't be charged twice, so please rest assured. If it still doesn't work, please contact us via the "Contact Us" button at the top right.
We apologize for the inconvenience.