Resolve ‘This item is no longer available’ when adding Item to Cart in Web Store

The error “This item is no longer available” is displayed if the item being added to the cart is no longer available.

Solution

1. Navigate to Commerce > Websites > Website List> Shopping tab
2. Enable Include Out Of Stock Items checkbox
3. In the Item record > Web Store sub tab > Stock and Pricing Behavior section, set to either -Default-, Remove item when out-of-stock or Allow back orders with no out-of-stock message