We're sorry for the trouble. This can sometimes happen due to a temporary issue with Google Play's servers.
Please restart your device and open the app again. If it still doesn't take effect, tap "Restore Subscription" on the screen that opens from the crown icon. 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 with the details using the "Contact Us" button at the top right.