Resolve the 404 Not Found/Page Not Found Error when Trying to Add an Item to the Cart on a WSDK Site

Scenario:
When Shoppers access a WSDK site and adds an Item to the Cart, they get a 404 Not Found/Page Not Found Error.

Solution:

Given that the Customer had setup their WSDK site correctly and in accordance with the steps provided in the Help Center article "Setting Up an External Catalog Site" another thing to check is if there is a Domain set up for their NetSuite WSDK site and selected it as it's Primary Web Site URL.

When a Domain is setup and a default Primary Web Site URL is selected on a NetSuite WSDK site, the WSDK Item scripts generated in NetSuite to embed on your External Site does not generate or update its SRC attribute with your default NetSuite Web Store domain. Notice that the SRC attibutes remain as 'http://shopping.netsuite.com/' instead of 'http://www.yourdomain.com/'.  This is the reason why adding items to the Shopping Cart causes the Page Not Found error or even displaying certain item details will not show any value. 

To resolve:
1. Navigate to Setup > Site Builder > Set Up Web Site
2. In the Domains tab, ensure that the Primary Web Site URL option is not marked.