Nope, it's a Facebook issue. Have you checked your FB App notification settings? If the 'Activity About You' isn't active for PUSH notifications, you get pretty much no notifications. You further need to make sure that the PUSH settings are on and configured to your liking at the bottom of that settings page.
I am also not receiving notifications on the Facebook app icon.
When I open the app all the notifications are there.
Just not on the S9 home screen icon.
All my other apps are receiving notifications just fine. It's only Facebook that has the problem.
I have gone through all the notification settings on the Facebook
app and on the phone settings itself.
All of the notifications were showing up correctly on my former Samsung Galaxy S8 but since switching to the S9 there is nothing.