Error: Inventory-based listing management is not currently supported by this tool

This operation is not allowed for inventory items.  Inventory-based listing management is not currently supported by this tool. Please refer to the tool used to create this listing

There is a problem with certain eBay listings that have been created using a different tool, such as the Shopify eBay channel, which uses a different set of APIs, known as the 'Inventory APIs'These APIs are not compatible with the 'Trading' APIs, which are used by Salestio and most of the other tools. 

This means that these listings cannot be updated using Salestio or any other tool that uses the Trading APIs, including the normal 'Sell Your Item' flow on eBay.  In other words, it even can't be edited on eBay's UI.

Salestio is unable to use the new APIs because they are not fully featured and do not allow merchants to perform all necessary operations to manage their listings, edit it in ebay UI or using additional special options.

The only solution to this issue is to stop the original listings created with Inventory API (e.g. created by Shopify Ebay App) and then create new listings using Salestio or another compatible tool (it's possible to create listing directly on ebay UI).

If you would like to learn more about how to create new ebay listings with a Salestio please check this article from our blog — https://salest.io/blog/page/create-ebay-listings-using-salestio-t-shirt-dropshipping-on-shopify