Amazon's eCommerce System (ECS4) is now known as the Product Advertising API and it has new requirements for access.
Join Amazon Associates to get an Associates ID - if you already have one, use that. BizStore now allows you to operate with an associates ID for each country, should you wish.
If you don't want to get involved as an Amazon associate, but just wish to use the module as a service to your members, it will function with the preset Associate IDs provided.
Either way, you MUST have a valid Access Key, Secret Key and Associates ID for BizStore to work.