Not receiving any notifications from Instagram after updating to iOS 12? Well, it is not necessarily an iOS 12 issue but definitely an iOS problem because it has happened to a lot of users in the past.
You can check Instagram notifications setting for your iPhone by going to Settings » Notifications » Instagram
In case the Instagram app is missing under Notifications setting on your iPhone, then you need to delete the Instagram app and re-install to fix the Notifications problem.
- Hold the Instagram app icon from Home screen on your device until it jiggles.
- Tap the cross icon over the app icon.
- Tap Delete to remove the app from your iPhone.
- Open App Store, search for Instagram and download the app again.
Now go to Settings » Notifications » Instagram to make sure everything is normal again.