Messenger app not showing pop up notifications

[AC Question]

I have a galaxy s6 running marshmallow. Yesterday I updated the Facebook messenger app, but the emojis now look so ugly that I downgraded the app with an apk. I've tried numerous versions from different sources, but all these do not show pop up notifications like my other apps. The little icon shows in my status bar, and the notification is there when I pull down the notification bar, but I don't get pop ups for some reason. Notification settings are on both in settings and in the app so I don't understand what's going on.