Error 99010: A value is missing... [country_of_origin = null].
Amazon recently introduced an additional mandatory field, Country of Origin as explained here: https://sellercentral.amazon.co.uk/gp/help/external/help.html?itemID=ASP7CFPVS9UCWKR&language=en_GB&ref=efph_ASP7CFPVS9UCWKR_relt_G23531
As long as the country of origin field will be empty, you will get that kind of error:

For that reason, we introduced a new Rule in the Rules > Inventory tab that allows updating the country of origin in bulk.
You just have to create a Rule for the group of products you want, it can be based on Vendor, Collections, etc.;
Here is a sample rule for one Vendor:

Please note that the country has to be entered by its Alpha 2 ISO country code (2 letters); https://en.wikipedia.org/wiki/List_of_ISO_3166_country_codes
For instance, if you have many vendors manufacturing their products in China, you can make more comprehensive and compact rules such as the following examples;
A set of manufacturers:

Please be attentive to the "Any" condition, it could match all your products if it is wrongly used.
A collection:

Once configured, you can export again in Action > Catalog > Export and then verify your Feed result in the Feeds tab.
As long as the country of origin field will be empty, you will get that kind of error:

For that reason, we introduced a new Rule in the Rules > Inventory tab that allows updating the country of origin in bulk.
You just have to create a Rule for the group of products you want, it can be based on Vendor, Collections, etc.;
Here is a sample rule for one Vendor:

Please note that the country has to be entered by its Alpha 2 ISO country code (2 letters); https://en.wikipedia.org/wiki/List_of_ISO_3166_country_codes
For instance, if you have many vendors manufacturing their products in China, you can make more comprehensive and compact rules such as the following examples;
A set of manufacturers:

Please be attentive to the "Any" condition, it could match all your products if it is wrongly used.
A collection:

Once configured, you can export again in Action > Catalog > Export and then verify your Feed result in the Feeds tab.
Updated on: 14/01/2025
Thank you!