Here are the instructions that Apple give how to correct a problem with push notifications.
If you’re not getting notifications for a specific app, try these steps:
- Go to Settings > Notifications, select the app, and make sure that Notifications are turned on.
- Make sure that you’re signed in to your Apple ID on your iOS device. Go to Settings > iTunes & App Stores and enter your Apple ID and password.
- Make sure that Do Not Disturb is turned off. Go to Settings > Do Not Disturb and tap Manual if it's turned on.
- If you’ve recently installed an app, open the app.
Do you receive test notifications?
Have you tried resetting the connection with the above link?