Node/Express API runs locally but hangs up on API call in AWS Lambda

I have an Express API setup which works fine locally. However, when deployed to AWS Lambda it chokes/hangs on a call to an Authorize.net API and the Lambda function closes. Lambda/Cloudwatch logs don't indicate an error of any kind.

• Other external API calls work as expected if problematic API call is circumvented.
• CORS is installed and enabled on the Express app, so I don't think that is the problem

Completely at a loss.

Any help is appreciated.

authnet-api.js

const axios = require('../config/axios')
const loginId = process.env.AUTHORIZENET_LOGIN_ID
const transactionKey = process.env.AUTHORIZENET_TRANSACTION_KEY

class AuthNetAPI {
  constructor() {
    this.headers = { headers: { 'Content-Type': 'application/json' } }
  }
  async getTransactionDetails(transactionId) {
    return axios.authNetAxios.post(
      '/',
      {
        getTransactionDetailsRequest: {
          merchantAuthentication: {
            name: loginId,
            transactionKey: transactionKey,
          },
          transId: transactionId,
        },
      },
      this.headers
    )
  }
}
module.exports = new AuthNetAPI()

webhook controller

const moment = require('moment')
const AuthNetAPI = require('../lib/authnet-api')
const helpers = require('../utils/helpers')


module.exports.makeWebhookPayment = async (req, res, next) => {
  try {
    const rawBodyString = req.rawBody
    const notificationBody = req.body
    const authNetHash = req.header('X-ANET-Signature')
    const clientHash = await helpers.generateHash(rawBodyString)
    const timestamp = Date.now()
    const batch = `AuthorizeNet_Phone ${moment(timestamp).format('M/D/YYYY')}`
    const documentDate = moment(timestamp).format()

    if (authNetHash === clientHash) {
      res.sendStatus(200)
      const transactionId = req.body.payload.id

      console.log(transactionId) // this logs out.

      const transactionResult = await AuthNetAPI.getTransactionDetails(
        transactionId
      ) // this API call closes the Lambda function with no error

      const transaction = transactionResult.data.transaction
      // console.log(transaction) // this does not log out, obviously.

     ...// remainder of code
 
  } catch (error) {
    next(error)
  }
}

index.js (express app wrapped with serverless-http handler)

const serverless = require('serverless-http')
const app = require('./src/config/express')

process.env.ENVIRONMENT === 'production'
  ? (module.exports.handler = serverless(app))
  : app.listen(3000, () => {
      console.log('listening on port 3000')
    })

module.exports.handler = serverless(app)