I had the same problem with the screen overlay detected error which didn't allow me to give permissions to a whole bunch of apps. rendering them useless. I tried everyone of the suggestions recommended on this site, to no avail. Finally, after speaking to Sprint about yhe problem on my Galaxy S7 Edge, a smart tech at a Best Buy store at the Samsung dept. asked if I had downloaded any security apps. which I had. Clean Master and Battery Doctor. Once she got rid of them because the interfered with the built in Knox security, everything started working fine.