我正在尝试整合贝宝的在线快速结账体验，但我被这个错误困住了。 下面是我正在测试的代码:

axios
  .post(
    "https://api-3t.sandbox.paypal.com/nvp",
    {
      USER: process.env.PAYPAL_USER,
      PWD: process.env.PAYPAL_PASSWORD,
      SIGNATURE: process.env.PAYPAL_SIGNATURE,
      METHOD: "SetExpressCheckout",
      VERSION: "124.0",
      PAYMENTREQUEST_0_CURRENCYCODE: "USD",
      PAYMENTREQUEST_0_AMT: "4.5",
      RETURNURL: "http://localhost:3000/pay",
      PAYMENTREQUEST_0_SELLERPAYPALACCOUNTID:
        "sb-47jx7i2598580@business.example.com",
    },
    {
      headers: {
        "Content-Type": "application/url-form-encoded",
      },
    }
  )
    .then((res) => {
      console.log("Got res", res.data);
    })
    .catch((err) => {
      console.error("Caught err", err);
    });

有人能帮我找出问题所在吗？