flipkart api issue

any one facing 

{"code":400,"message":"Unable to process JSON"}

Request:

{
    "type": "preDispatch",
    "filter": {
        "states": [
            "APPROVED",
            "READY_TO_DISPATCH"
        ],
        "locationId": ""
    },
    "pagination": {
        "pageSize": 50,
        "pageNumber": 1
    }
}

Response:

{"code":400,"message":"Unable to process JSON"}