Facebook Messenger won't show pop up notifications

[AC Question]

Messenger recently sent out a server side update to my phone that I absolutely hate. I can't stand it, so I uninstalled my app and installed an older version apk that seems unaffected by the new changes. However, I now don't get pop up notifications. The icon for a new message shows up in the status bar, but there's no pop up. The lock screen is unaffected. I have made sure that the app settings for notifications are now and so are the ones in App Info on my phone. I have a Samsung Galaxy s6, not rooted, on Android 6.0.1. I've tried numerous different versions of apks from several sources and have no idea why this is happening. Any ideas?