Activity level for a listing boosts the listing, so a single review in a year is not good. This platform may not be the best for your beautiful condo because it does not focus on high end homes. Have you ever listed with other platforms?
You could radically lower your price to be similar to other listings for a period of time and that should increase your activity level. Then when you get a couple of reservations, raise the rate. Also, you could lower your nightly rate for six guests and then add an extra guest fee for the 7-12 guests. That way , smaller groups would see the listing and larger groups would pay more. Just a thought