Why am I getting a fulfillment API error in Shopify?

[95100]

hello.
I am Yoo Gyeong-ok, a developer of the SHOPIFY API in Korea.
An error occurred while trying to proceed with the FULFILLMENT. It's so hard to find the error, please help.
"fulfillment_order_id" among the REQUEST API items. This is the FULFILLMENTS.ORDER_ID value of the order API brought from SHOPIFY. NOT FOUND in RESPONSE is too vague. TOKEN value was kept private.
Any help please?
thank you

(EXAMPLE)
Transferring URL : https://{url}.myshopify.com/admin/api/{version}/fulfillments.json

JSON :
{
"fulfillment": {
"line_items_by_fulfillment_order": [
{
"fulfillment_order_id": "5136674586861",
"fulfillment_order_line_items": [
{
"quantity": 1,
"id": "12967568081133"
}
]
}
],
"origin_address" : {
"address1" : "625 W 57th St",
"address2" : "",
"city" : "New York",
"country_code" : "US",
"province_code" : "NY",
"zip" : "10019"
},
"message": "The package was shipped this morning.",
"tracking_info": {
"number": "6596334662",
"company": "DHL Express",
"url": "https://www.dhl.com/us-en/home/tracking.html?tracking-id=6596334662"
},
"notify_customer": false
}
}

HEADERS : X-Shopify-Access-Token: {SHP_TOKEN}

response:
{
"errors": "Not Found"
}