I have a Samsung Galaxy S6, most likely running a version of Marshmallow (not sure how to check). For the first time ever, my screen overlay detected error (asking me to turn off all screen overlays before allowing permission changes) will not go away. I had Twilight installed and running, and I first disabled that since a simple disable of the app usually fixes the problem. Today it did not. I clicked show system apps from the More button on the top right, unclicked all apps in the list, system and otherwise, so that they were all gray. Attempted to allow permissions to no avail, as the phone still detected some screen overlay. All of my apps are unchecked for "Apps that can appear on top." I have no idea what else to try. I have restarted and cold booted. Any suggestions to turn of this mysterious screen overlay and allow changes to permissions?