Insert event in google calendar using service account with Nodejs

I can't insert an event using Nodejs with service account. The service account Email is already added into the account with the permission make changes to event My nodejs code is running on google cloud functions Here is my code:

const {
  google
} = require('googleapis');


var event = {
  'summary': 'Google I/O 2015',
  'location': '800 Howard St., San Francisco, CA 94103',
  'description': 'A chance to hear more about Google\'s developer products.',
  'start': {
    'dateTime': '2020-02-10T13:00:00-05:00'
  },
  'end': {
    'dateTime': '2020-02-10T15:00:00-05:00'
  },
  'attendees': [{
    'email': 'Emailh@domain.com'
  }],
  'reminders': {
    'useDefault': false,
    'overrides': [{
        'method': 'email',
        'minutes': 24 * 60
      },
      {
        'method': 'popup',
        'minutes': 10
      },
    ],
  },
};

exports.helloWorld = (req, res) => {
  google.auth.getClient({
    scopes: 'https://www.googleapis.com/auth/calendar',
  }).then(auth => {
    const calendar = google.calendar({
      version: 'v3',
      auth
    });
    calendar.events.insert({
      auth: auth,
      calendarId: 'MyCalendarID',
      resources: event,
    }, function(err, event) {
      if (err) {
        console.log('There was an error contacting the Calendar service: ' + err);
        return;
      }
      console.log('Event created: %s', event.htmlLink);
    });
  })

};

the same code works fine when I use the function read. Any Idea ?