Most of the time, offers are added to your account immediately after purchase. Occasionally, they may take a while to arrive. When this delay occurs, it means the purchase is still processing - this process can take up to 24 hours. No need to try and buy again now, your content should arrive soon!
Sometimes, all your device needs is a fresh connection with the servers. Try exiting the game and logging in again, this may speed the process along.
If you still haven’t received a purchase made more than 24 hours ago, please contact Google Support, as Google process all payments made toward the game on Android. You can reach them right here.
Also, you may want to reach out to your credit card provider about any pending charges, as purchases that could not be completed may have charges roll off within a few days.