If you want to load products with only a catalogue connected, you will need to make sure to adjust a couple settings. In the Filters, under Shipping there's a checkbox to "Allow products that can not be fulfilled by my warehouse distributors".
This setting will allow in the products even though you don't have a distributor connected. You will want to be aware when selecting brands and setting filters that the catalogue may have product data for products that are no longer available at all. You can filter these out using the various filters, or even using the Part Numbers filter to create a list of skus to keep out of the store.