> ## Knowledge Base Index
> Fetch the complete knowledge base index at: https://doc.common-services.com/sitemap.xml
> Use this file to discover available pages before exploring further.
> Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash).

# Duplicate entries are not allowed - Product skipped - Amazon Marketplace Plus

## Error: Duplicate Reference

Example log message:

||| Duplicate entry for product 01234567890 (1/0) - Previously used by: 1/0 - This is not allowed - Product skipped...

---

## Cause

The reference shown is used **more than once** in the database, which is not allowed.  
Each product and each combination must have a **unique reference** (see: [Validate your catalog structure](https://doc.common-services.com/en/article/validating-your-catalog-structure-amazon-marketplace-plus-d3xsyp/)).

---

## How to identify the duplicate product

1. Copy the reference from the error message.
2. Paste it into the PrestaShop search bar.
3. If duplicates exist, multiple results will appear:  
   ![PrestaShop Amazon Marketplace duplicated reference](https://storage.crisp.chat/users/helpdesk/website/-/3/f/a/8/3fa8ee645cd13200/prestashop-amazon-marketplace-_1rbz1s0.jpg)

**Important:** If the duplicate is a **combination reference**, it may not appear directly in the search.  
Check the **Combinations** tab of the product sheet found in the search results.

---

## Solution

Assign a **unique reference** to each product and combination as explained here:  
[Validate your catalog structure](https://doc.common-services.com/en/article/validating-your-catalog-structure-amazon-marketplace-plus-d3xsyp/).