Since that feature is geo-fenced, (just like the auto-raise suspension at this location) your Model X needs a fresh GPS lock on latitude and longitude data.
So go for a quick drive around a block or two, then park you Model X in your garage, and THEN override the obstacle detection sensors using the FWD physical button on the b-pillar or the button on the MCU screen. You should now see the option to "Fully Open At This Location" prompt.