Getting 'Invalid line item id' Error with Correct Line Item ID in eBay Fulfillment API

Question

I've been using the eBay Fulfillment API successfully for months to create shipments, but recently, I've encountered an issue that I can't seem to resolve. When attempting to create a shipment using the eBay Fulfillment API, I'm consistently receiving the following error:

Error Id : 32200 Invalid line item id: 'NO_THING_HERE'

The problem is, I'm confident that I'm sending the correct and valid line item ID in my request. Even when I deliberately send an incorrect line item ID, the error message remains the same, and it seems like the line item ID isn't being recognized by eBay's API.

Here's an example of the JSON request I'm sending:

{
    "lineItems": [
        {
            "lineItemId": "1005676*******",
            "quantity": 1
        }
    ],
    "shippedDate": "2023-08-27T15:26:06-07:00",
    "shippingCarrierCode": "USPS",
    "trackingNumber": "*****112062**********"
}