Destination country can't be blank

Hello ,
By using the Create a shipment API i have an issue,

here is the json i POST

{"destination_country_alpha2":"JPN","destination_city":"\u5927\u962a\u5e02\u4e2d\u592e\u533a","destination_name":"\u5c0f\u9593\u5eb7\u88d5","destination_address_line_1":"\u96e3\u6ce25\u4e01\u76ee1-60 27\u968e WeWork","destination_phone_number":"+81 070-1063-3603","platform_name":"Rakuten","platform_order_number":"373496-20191011-00000735","taxes_duties_paid_by":"Receiver","is_insured":"true","destination_postal_code":"5420076","destination_email_address":"[email protected]","items":[{"description":"Dry food and Supplement","category":"Health & Beauty","actual_weight":"999999999","height":"0","width":"0","length":"0","declared_currency":"JPY","declared_customs_value":5200,"sku":"001"}]}

As you can see, i have a value for destination_country_alpha2
but here is the error i got
{"Exceptions::ManagerError":"CloudShipmentManagerError - action: create_by_api - Destination country can't be blank"}

can you maybe help me on that .

Thank you
Best regards