如何在Node.js中使用Axios解决PayPal Webhook 401未经授权的错误?

我正在使用Axios将PayPal webhook集成到我的Node.js应用程序中,但在触发webhook时遇到了401未经授权的错误。以下是我收到的错误:

Error data: {
  name: 'UNAUTHORIZED',
  message: 'Authorization failed due to insufficient permissions.',
  debug_id: 'b02145e0fae22',
  details: [
    {
      issue: 'PERMISSION_DENIED',
      description: 'You do not have permission to access or perform operations on this resource.'
    }
  ]
}
Error status: 401
Error headers: Object [AxiosHeaders] {
  // headers omitted for brevity
}

以下是我处理webhook事件的服务器端代码的简化版本。这个片段的重点是验证webhook签名和处理事件。

require('dotenv').config();
const express = require('express');
const axios = require('axios');

const paypalRouter = express.Router();

paypalRouter.post("/subscriptions/webhook", async (req, res) => {
  console.log("Received headers:", req.headers);
  const verification = {
    auth_algo: req.headers['paypal-auth-algo'], 
    cert_url: req.headers['paypal-cert-url'], 
    transmission_id: req.headers['paypal-transmission-id'],
    transmission_sig: req.headers['paypal-transmission-sig'],
    transmission_time: req.headers['paypal-transmission-time'], 
    webhook_id: process.env.WEBHOOK_ID,
    webhook_event: req.body,
  };

  const params = new URLSearchParams();
  params.append("grant_type", "client_credentials");
  const authResponse = await axios.post("https://api-m.sandbox.paypal.com/v1/oauth2/token", params, {
    headers: {
      "Content-Type": "application/x-www-form-urlencoded",
    },
    auth: {
      username: process.env.PAYPAL_CLIENT_ID,
      password: process.env.PAYPAL_SECRET,
    },
  });

  const access_token = authResponse.data.access_token;
  const verifyResponse = await axios.post("https://api-m.sandbox.paypal.com/v1/notifications/verify-webhook-signature", verification, {
    headers: {
      'Content-Type': 'application/json',
      Authorization: `Bearer ${access_token}`
    },
  });

  if (verifyResponse.data.verification_status === "SUCCESS") {
    console.log("Webhook verified");
    // more code 
 } else {
    console.error("Webhook verification failed:", verifyResponse.data);
    return res.status(401).send('Webhook signature verification failed');
  }
});

module.exports = paypalRouter;

我需要帮助的是:

1. 理解为什么尽管身份验证和权限设置看似正确,但401错误仍会发生。

2. 如何确保我与PayPal的webhook验证步骤正确实施。

我已经尝试查看PayPal的官方文档,并确保所有权限和API凭据都得到了正确配置。错误仍然存在,我不确定如何进一步调试。