The error may arise if:
- you rename an existing variation option in Magento using a different capitalization, e.g. from "white" to "White". Once the option is updated, M2E sends both old and new option values to eBay. The old option is marked as 'Will be deleted' and the new - as 'Will be added'. Since the option values are the same but have different capitalization the error is returned.
To resolve the issue, you need to edit your Magento Product variations in accordance with the relevant eBay Item variations.
- you submit an Item with the same variation options but written in the upper- and lowercase simultaneously, e.g. "white", "White", and "WHITE". eBay recognizes the values as duplicates and prevents the Item from submitting.
To resolve the issue, edit your Magento Variational Product accordingly.