If you go to Admin on the left and then Administrators in the lower left, do you see multiple users in the top left?
If so, are you able to log into those and see if the Notification is on one of them?
The reason I say this is I believe the notifications may be user dependant. So if you set them up for the default Admin account you won't see them on a new account called "kornholio".
If that doesn't pan out than unfortunately I don't have any idea why the notification wouldn't show. Would require some digging into logs to determine the cause.