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.**