TI-API: Invalid Customer "Customer is not valid. If you are still having issues, contact TI customer support

We are integrating the Backlog API for our company. However, we have encountered an issue and need your assistance. When we post to create an order as follows:

{
  "order": {
    "customerPurchaseOrderNumber""TestPO-230405-01",
    "checkoutProfileId""348F38Axxxxx",
    "lineItems": [
      {
        "customerLineItemNumber""1",
        "tiPartNumber""SN74LS00N",
        "customerAnticipatedUnitPrice":1.2,
        "quoteNumber""26936554",
        "customerCurrencyCode""USD",
        "schedules": [
          {
            "requestedQuantity"3000,
            "requestedDeliveryDate""2025-05-26"
          }
        ]
      }
    ]
  }
}
we got the the following issues
{
    "orders": [
        {
            "messages": [
                {
                    "code""TI-TXT-025",
                    "type""ERROR",
                    "reason""Invalid Customer",
                    "message""Customer is not valid. If you are still having issues, contact TI customer support https://support.ti.com/csm"
                }
            ],
            "customerPurchaseOrderNumber""TestPO-230405-01",
            "orderStatus""REJECT",
            "lineItems": [
                {
                    "tiPartNumber""SN74LS00N",
                    "customerLineItemNumber""1",
                    "itemCheckoutProfileId""348F38xxxx",
                    "status""Rejected",
                    "tiTotalOrderItemQuantity"0,
                    "customerAnticipatedUnitPrice"1.2,
                    "customerCurrencyCode""USD",
                    "quoteNumber""26936554",
                    "schedules": [
                        {
                            "requestedQuantity"3000,
                            "requestedDeliveryDate""2025-05-26"
                        }
                    ]
                }
            ]
        }
    ]
}