Simply setting up Carriers does not mean they always show up as a selectable option on the checkout page. Carriers that use a Rating Service, such as FedEx and UPS, require products to have an identified weight before the carriers appear on the website. All products have 0 (zero) as the default weight, which is not an acceptable weight value for the rating service to work correctly.
- To add a weight value to a product manually, go to Admin Console > Catalog > Products.
- Click Edit next to the desired Products.
- Scroll down to the Shipping section.
- Enter the correct Shipping Weight: