Account API v1 createFulfillmentPolicy ERR 20500

[hakiaio]

Here is my request payload that is being sent from my application. 

{
    "name": "Domestic free shipping",
    "marketplaceId": "EBAY_US",
    "categoryTypes": [
        {
            "name": "ALL_EXCLUDING_MOTORS_VEHICLES"
        }
    ],
    "handlingTime": {
        "unit": "DAY",
        "value": "2"
    },
    "shippingOptions": [
        {
            "costType": "FLAT_RATE",
            "optionType": "DOMESTIC",
            "shippingServices": [
                {
                    "buyerResponsibleForShipping": "false",
                    "freeShipping": "true",
                    "shippingCarrierCode": "USPS",
                    "shippingServiceCode": "USPSPriorityFlatRateBox"
                }
            ]
        }
    ]
}

in which I am sending to https://api.ebay.com/sell/account/v1/fulfillment_policy (production)

and keep receiving 

{
    "error": {
        "errors": [
            {
                "errorId": 20500,
                "domain": "API_ACCOUNT",
                "category": "APPLICATION",
                "message": "System error."
            }
        ]
    }
}

I even tested on https://developer.ebay.com/my/api_test_tool?index=0&api=account&call=fulfillment_policy__POST&variat... with the working example and all samples on the documentation for https://developer.ebay.com/api-docs/sell/account/resources/fulfillment_policy/methods/createFulfillm... but still receive the above error. I can't find anything upon the API status page does anyone know what's going on?