Screen overlay s6 fail

[AC Question]

Unable to change permission on apps through setting. Dialog pops up with message 'to change permission setting you first need to turn off screen overlay from settings>apps'.
It takes me to overlay screen and i turn it off. But when i go back to app to change permission the same message keeps on appearing to turn off screen overlay
What is wrong??

 

[Chromelassie]

Read that Clean Master caused it. I don't know why. I deleted the app and no problems so far