We're sorry for the trouble. This can sometimes happen due to a temporary issue with Google's servers.
Please restart your device and open the app again. If it still doesn't take effect, open "Premium" in the settings and tap "Restore Subscription" (if the purchase screen appears instead, tap "Restore (Already Purchased)"). You won't be charged twice as long as you use the same Google 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.