If it's Chrome make sure you exit all instances. You might have that background Chrome thing running (little Chrome icon near the clock) so even if your close Chrome it won't apply.
Did a restart. Still not working. Not sure what I'm doing wrong. This is meant to eliminat the scroll bar right?
clicked google chrome - open file location - right clicked on chrome -> properties, -> shortcut -> went to target: changed it to the following:
Tartget: "E:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --enable-features=OverlayScrollba