This means that something you have downloaded is blocking your access to the option. Do you recall anything specific that was downloaded at the time this started happening?
This helped me solve my problem👍👍 I know now it was because of my launcher (evie). I loved the launcher but i dont get why i couldn't use some gestures. Deleted the launcher and everything works perfect. Thank you for the answer sir.
My phone did the same after the first patch for Samsung one ui android 9. I loved the full screen gestures and now my quick settings has the navigation bar setting to hide it but it's always half lit and you cant turn it on or off.
I think I found the problem as this was bugging me to no end. It seems to be related to the "Accessibility" functions. Try this Settings>Accessibility>Installed Services>Accessibility Menu: Turn OFF. Then go back the to Navigation Bar Settings and you should find the full screen gestures option available again. The Navigation Bar the Notification Menu Buttons drawer should also work to turn this on and off.