Filtration Group 1" Furnace Filters

You do not have a link list with a handle set to filtration-group-1-furnace-filters, or you do and it's empty. Go ahead and create a link list called Filtration Group 1" Furnace Filters 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 filtration-group-1-furnace-filters.