Selling-partner - Access to requested resource is denied. (Fulfillment-outbound-api: createFulfillmentOrder)



I’m using SP-API (Selling Partner API) to create a fulfillment order. I’ve been following the documentation from here:

But I get an error response:
Exception in thread “main” io.swagger.client.ApiException: {
“errors”: [
“message”: “Access to requested resource is denied.”,
“code”: “Unauthorized”,
“details”: “”

My developer account has access to Amazon Fulfillment, and the application I have created has the same role assigned to. I have been able to successfully make calls to the Orders and Feeds API. But any calls to the Fulfillment Outbound results in this error message.