Starting with Android Marshmallow, there’s a curious error that sometimes shows its face, but it can be hard to decipher what’s causing it. The “screen overlay detected” error is a troubling one since it won’t allow certain apps to launch, but it’s even more frustrating because it’s hard to find what’s causing it.
Fortunately, it’s a pretty easy fix once you know what’s causing the error: a feature found in Marshmallow and beyond that allows apps to “draw” over other apps. For example, Facebook Messenger uses chat heads to stay in the foreground of whatever you’re doing—this is the app using the “Draw over other apps” feature. In other words, it’s a screen overlay. It’s already starting to click, isn’t it?