Google Ads API with Google Apps Script no access token received - google-apps-script

Question

I am trying to use Google Ads on Google Apps Script using this guide. I created client id and client secret on Google Console's API & Services.
Not too sure if this configuration is correct but the account is linked to Google Apps Script as I have pagespeed insights as well and there are some requests on the dashboard. I added https://www.googleapis.com/auth/drive as the scope. Again not too sure if I should add Google Ads to the scope. Lastly, got my refresh token from Google Auth playground. When I run the script above I got the following error:
Error: No access token received: {
"error": "invalid_client",
"error_description": "Unauthorized"
}
authenticate_ # test.gs:120
withRefreshToken # test.gs:144
initializeOAuthClient # test.gs:28
Honestly not too sure what I am doing wrong here so any help would be very much appreciated. Thank you.
Edit
Codes:
//From Google Console API & Services
var CLIENT_ID = '"MY_CLIENT_ID';
var CLIENT_SECRET = 'MY_CLIENT_SECRET';
//From Google Authplayground
var REFRESH_TOKEN = 'REFRESH_TOKEN';
// Enter scopes which should match scopes in File > Project properties
// For this project, e.g.: https://www.googleapis.com/auth/drive
var SCOPES = "https://www.googleapis.com/auth/adwords";
// Script ID taken from 'File > Project Properties'
var SCRIPT_ID = 'MY_SCRIPT_ID';
var authUrlFetch;
// Call this function just once, to initialize the OAuth client.
function initializeOAuthClient() {
if (typeof OAuth2 === 'undefined') {
var libUrl = 'https://developers.google.com/google-ads/scripts/docs/examples/oauth20-library';
throw Error('OAuth2 library not found. Please take a copy of the OAuth2 ' +
'library from ' + libUrl + ' and append to the bottom of this script.');
}
var tokenUrl = 'https://accounts.google.com/o/oauth2/token';
authUrlFetch = OAuth2.withRefreshToken(tokenUrl, CLIENT_ID, CLIENT_SECRET,
REFRESH_TOKEN, SCOPES);
}
/**
* Execute a remote function.
* #param {string} remoteFunctionName The name of the function to execute.
* #param {Object[]} functionParams An array of JSON objects to pass to the
* remote function.
* #return {?Object} The return value from the function.
*/
function executeRemoteFunction(remoteFunctionName, functionParams) {
var apiParams = {
'function': remoteFunctionName,
'parameters': functionParams
};
var httpOptions = {
method: 'POST',
headers: {
'Content-Type': 'application/json'
},
payload: JSON.stringify(apiParams)
};
var url = 'https://script.googleapis.com/v1/scripts/' + SCRIPT_ID + ':run';
var response = authUrlFetch.fetch(url, httpOptions);
var data = JSON.parse(response.getContentText());
// Retrieve the value that has been returned from the execution.
if (data.error) {
throw Error('There was an error: ' + response.getContentText());
}
return data.response.result;
}
// Paste in OAuth2 library here, from:
// https://developers.google.com/google-ads/scripts/docs/examples/oauth20-library
I have pasted the oauth2.0 library under the codes above.
Edit 2
I fixed the part of function initializeOAuthClient. It now shows execution complete, but when I try to run function executeRemoteFunction I am getting TypeError: Cannot read property 'fetch' of undefined. I am guessing I have to input remoteFunctionName and functionParams but where do I find them?