You will see this message when you are trying to save the changes of product details. When you saw this error, please check the fields below for the product.
1. SKU / Model (The main SKU) must be unique and mandatory. It contains only alphabet, number or special character with -.
2. Option SKU must be unique and mandatory if you have generated for the product. It contains only alphabet, number or special character with -. You can either click Generate SKU button to auto generate or fill in yourself.
3. SEO Friendly URL must be unique. It would happen when you are trying to create a product with the same name you have created before, system will auto generate the SEO Keyword according to the product name, hence it can’t be saved when it detects duplicated SEO Keyword. Please update SEO Friendly URL.