This error occurs when you are providing an invalid product type to Amazon. You need to provide the correct value for the product type, which is defined in the flat file template or Amazon xsd.
If you are using flat file templates,
1- Click edit template and find “feed_product_type” field in the template.
2- Write the possible option as free text.
3- Save and close the template.
4- Send product data update and sync the channel.
If the issue hasn’t been resolved then try to download the related flat file template from your Amazon seller Central account and upload this template into StoreAutomator. The template may have been updated by Amazon.
If you are using xml templates,
These instructions are also valid for xml templates. You need to make sure that the product type contains valid values and that these are provided.
If you still encounter the same issue after correcting everything, please open a case with Amazon in order to update their xsd.