Apps no longer appearing on top

[Android Central Question]

I don't know sonce when but I've noticed that overlay apps such as Facebook Messenger chat heads and Musixmatch no longer appear on top of my screen. Though when these apps are active, there is a notification saying that the overlay is there.
I've tried disabling them in "apps that can appear on top" in settings then re enabling them andreinstalling the apps but nothing. Anyone got a solution or advice?