Error: Duplicate UUID used.
The specified UUID has already been used; ListedByRequestAppId=xxx, item ID=xxx.
The eBayIntegration for Zen Cart Plug-in assigned a unique identifier (UUID) to each store product and listing. This is used to prevent accidental duplicate listings. Generally, when you see this error it means that the plug-in and eBay prevented a duplicate listing on eBay,
When you see this error, you should run the Orphan Check Tool on the Tools Tab. It will ensure that items listed on eBay are properly linked to store products in Zen Cart.
If a product produces this error when you are trying to add it to eBay and you have ensured that it is not currently listed on eBay, then you can assign a new UUID to the store product. Edit the product in the Products Tab and attempt to add it to eBay. After the add fails click the "Messages" button, Beside the UUID error message is a button allowing you to change the product's UUID.