i had this issue, and just solved it, i think. I'm on Galaxy S7 Edge. First I went to settings and went to applications, then noticed a strange app with a blank icon, i couldn't unninstall it nor force stop it. Then went to some forums like this one and foind that it may be a malware. Went to play store and downloaded Malwarebytes, ran the scan, and found 1 malware, that one with the blank icon, then i realized that i didn't need the Malwarebytes, just search for administr... on setting, to find 'Device administrators', i noticed that the blank app was a admin, that's why i couldn't unninstall it. Thats it!