Hi. New here. Not sure of my wifes model, but also a Galaxy. We both have the same issue. A lot of times when a contact replies within a couple minutes, we do not get notification. I say, a lot of times, because it seems to be intermittent. One day we'll get notifications, other days not. Seems to occur mostly with popular contacts. I've combed through settings but haven't found anything to get notifications with all replies.