Bulk item via Walmart API

Question

I try bulk item by Walmart API, but i get error: There was an unexpected error that occurred while setting up this product. Please try to ingest this item again.

I use PHP and this my json:

  {
    "MPItemFeedHeader": {
        "version": "3.2",
        "requestId": "1606485958",
        "requestBatchId": "1606485958"
    },
    "MPItem": [{
        "processMode": "REPLACE_ALL",
        "feedDate": "2020-11-27T14:05:58Z",
        "sku": "2663d9467e64a0a94ab0eeeccd9f37dd",
        "productIdentifiers": [{
            "productIdType": "UPC",
            "productId": "3212971916"
        }],
        "MPProduct": {
            "productName": "3x Micro USB Fast Charging Charger Cable Cords For Samsung Galaxy S4 S7",
            "category": {
                "Electronics": {
                    "ElectronicsAccessories": {
                        "shortDescription": "Store category\r\n...",
                        "mainImageUrl": "https:\/\/i.ebayimg.com\/images\/g\/UGUAAOSwU8hY7awi\/s-l1600.jpg",
                        "brand": "Unbranded"
                    }
                }
            }
        },
        "MPOffer": {
            "price": 31.68
        }
    }]
}

where error? What happened?