You do not have a link list with a handle set to bmw-series-5-e28-1981-1988, or you do and it's empty. Go ahead and create a link list called BMW Series 5 E28 (1981 - 1988) on your Navigation page and populate that link list with links that point to collections, to see collections listed here. Make sure the link list also has a handle set to bmw-series-5-e28-1981-1988.