can't save my video settings? no "Apply Changes"

Hey as my title states, I've been trying to adjust my video settings but I can't. I get no apply changes option when i change anything. I want to do borderless full screen but I can't. I read only that the settings file could be set on read only but i checked that off and nothing happens. on top of that, I've tried to read only on the entire folder, but it just resets. not sure what's going on.