Shipping - The weight attribute is not being taken

I have a problem with the integration with FedEx.

My button look like this:

<button

  data-v-20f24064=""

  data-item-id="emma"

  data-item-price="20"

  data-item-url="/shop/emma"

  data-item-description=""

  data-item-image="https://theironfairies-files.s3.ap-southeast-1.amazonaws.com/if_photos_fairies_0006_Emma_4b00329746.jpg"

  data-item-name="Emma"

  data-item-weight="200"

  data-item-length="3"

  data-item-height="15"

  data-item-width="11"

  class="snipcart-add-item text-yellow"

>

  Add to cart


</button>

And I can see the JSON submitted to Snipcart is:

{

    "uniqueId": "4673998b-ebde-4eb5-a563-9d76451dded0",

    "token": "",

    "id": "emma",

    "name": "Emma",

    "price": 20,

    "description": "",

    "hasTaxesIncluded": false,

    "categories": [],

    "url": "https://www.theironfairies.com/shop/emma",

    "fileGuid": null,

    "image": "https://theironfairies-files.s3.ap-southeast-1.amazonaws.com/if_photos_fairies_0006_Emma_4b00329746.jpg",

    "quantity": 3,

    "quantityStep": 1,

    "minQuantity": null,

    "maxQuantity": null,

    "stackable": true,

    "shippable": true,

    "taxable": true,

    "taxes": [],

    "customFields": [],

    "duplicatable": false,

    "downloadLink": "",

    "metadata": null,

    "alternatePrices": {},

    "dimensions": {

        "weight": 200,

        "length": 3,

        "height": 15,

        "width": 11

    },

    "unitPrice": 20,

    "totalPrice": 40,

    "totalPriceWithoutTaxes": 40,

    "totalPriceWithoutDiscountsAndTaxes": 40,

    "totalPriceWithoutDiscountsAndTaxesLegacy": 40,

    "addedOn": 1659421592,

    "initialData": "",

    "modificationDate": 1659422150,

    "pausingAction": "None",

    "cancellationAction": "None",

    "isRecurring": false,

    "isRecurringV2": false,

    "isRecurringV3": false,

    "availablePlans": [],

    "selectedPlanId": "",

    "paymentGatewayId": "",

    "state": {

        "committing": false

    },

    "basePrice": 20

}

But anyway the integration with FedEx failed and I get an error saying there is not shipping rates… I have checked the developer logs and the error says:

Since no weight was specified, free shipping is returned. Make sure you specify the product dimensions. Products – Snipcart Documentation

Any idea what I am doing wrong?