Cannot use "target champions only"

This has been a bug for a while now. I config target champions only to one of my mouse buttons and it does nothing what so ever. My mouse button is working because I can hotkey it to anything else. This is a problem on both of my computers and I have tried re installing as well. This is a very annoying bug for yasuo players because it is almost impossible to wall jump with your e without the target champions only function.