WHAT IT MEANS
The shipping country on the order doesn't match the FBA region.
WHAT CAUSED IT
The shipping address is incompatible with the FBA warehouse either due to your FBA account settings or to their specific policies for the region.
HOW TO FIX IT
Send the order to the FBA region that supports the shipping country.
If the shipping address on the order matches the FBA region and the error is more specific, like "Value FRA for parameter CountryCode is invalid", double check that the shipping address country code is correct and only two digits.
Some FBA regions will ship internationally if you have export enabled with them, however they will typically only ship media items. If any other items are included in the order, they won't accept the order. Contact FBA for more details about what international shipping might be available for the regions you use.