App missing from iPhone Notifications Settings

Please help me solve this: an installed app that supports notifications does not appear in the list of apps under Settings > Notifications. The Amazon App is not present in my Settings > Notifications area, which means I am unable to receive notifications from this app. I have already tried deleting and re-installing the app.

iPhone 6 64GB Space Gray (GSM) AT&T MG4W2LL/A

iOS 9.2.1