In iOS, a system dialog may appear seeking your approval to grant the developer permission to send you notifications:

If you've accidentally clicked Don't Allow, here is how you can reset notifications for that app:

1. Open the Settings app.

2. Scroll to find the app you want to allow to notify you.

3. Tap on the Notifications setting to customize it.

4. Tap on Allow Notifications to authorize the developer of the app to send you notifications. You can also customize where alerts will be displayed (Lock Screen, Notification Center, Banners), and whether you want the app to use Sounds and Badges.

5. Close and relaunch the app from your Home Screen!