A slow internet connection or loading lag can result in foliage not appearing on the map. If you see the grey land grid, but your parcels do not appear highlighted at your location, restart your game to reload the map.
Though you may not see parcels visibly on the map, this is a visual glitch only, and does not affect rent or parcel ownership. These parcels cannot be repurchased by any player, and all parcels owned in your game profile are generating virtual rent.