This listing is a duplicate of an item you already have on eBay

This error suggests that the listing you are attempting to send to eBay is for an Item that is already on the marketplace. According to eBay policy, listing identical offers from the same seller at the same time is not allowed.

Please remove the duplicate listing not to violate eBay regulations. 

If the listing duplicate is identified in error, please make sure your product details, like title, brand, description, etc. are different from the ones that you have listed on the channel.