Express Js using simple-oauth2 to access Microsoft Graph, possible proxy issue?

Question

I have been following the tutorial posted here

https://learn.microsoft.com/en-us/outlook/rest/node-tutorial

to teach me how to access the Microsoft Graph API.

I have been working on my project at home and at work, and while the example works perfectly at home, I am unable to get an oAuth2 token while at work.

It all works up to this point

async function getTokenFromCode(auth_code) {
  let result = await oauth2.authorizationCode.getToken({
    code: auth_code,
    redirect_uri: process.env.REDIRECT_URI,
    scope: process.env.APP_SCOPES
  });

  const token = oauth2.accessToken.create(result);
  console.log('Token created: ', token.token);
  return token.token.access_token;
}

exports.getTokenFromCode = getTokenFromCode;

where the GET request for the token returns with status 200 but complains about an unhandled promise, so I have rewritten this section to be;

async function getTokenFromCode(auth_code, res) {
  const tokenConfig = {
    code: auth_code,
    redirect_uri: process.env.REDIRECT_URI,
    scope: process.env.APP_SCOPES
  };
  try {
    let result = await oauth2.authorizationCode.getToken(tokenConfig);
    const token = oauth2.accessToken.create(result);
    saveValuesToCookie(token, res);
    return token.token.access_token;
  } catch (error){
    console.log('Access Token Error:',error.message);
  }
};

exports.getTokenFromCode = getTokenFromCode;

This now fails with "Client request error: ECONNREFUSED (some ip):443" where (some ip) changes every time but appears to be a Microsoft server e.g. 40.112.64.18:443

The credentials I am using for the request are as in the tutorial;

const credentials = {
  client: {
    id: process.env.APP_ID,
    secret: process.env.APP_PASSWORD,
  },
  auth: {
    tokenHost: 'https://login.microsoftonline.com',
    authorizePath: 'common/oauth2/v2.0/authorize',
    tokenPath: 'common/oauth2/v2.0/token'
  }
};
const oauth2 = require('simple-oauth2').create(credentials);

I have tried doing the same request at work using Postman, following the setup here

Postman could not complete Oauth2 login for Microsoft Graph OAuth2

but the request hangs at a white screen after logging in.

As far as I know the proxy at work allows request from localhost (127.0.0.1) and I am able to request a code from the auth server so I am unsure why I am unable to request a token?

I have tried turning on proxy handling in express using;

app.set('trust proxy',true);

in the app.js but this does not seem to have any effect.

Any guidance will be gratefully received.