fullcalendar v５でgooglecalendar側の予定の追加

fullcalendar v5でgooglecalendar側にイベントの追加ができません
fullcalendarには予定追加できるのに反映がされません
※実際にはAPIとgooglecalendar idは入力されています

<?php
session_start();
require_once '../classes/UserLogic.php';
require_once '../functions.php';


//ログインしているか判定し、していなければ新規登録画面へ返す

$result = UserLogic::checkLogin();

if(!$result) {
    $_SESSION['login_err'] = 'ユーザを登録してログインしてください';
    header('Location: signup_form.php');
    return;
}

$login_user =$_SESSION['login_user'];

if(isset($_POST['keep'])) {
    $keep = $_POST['keep'];
    echo $keep;
}




?>
<!DOCTYPE html>
<html>
<head>
<title>カレンダー</title>
<meta charset='utf-8' />
<link href='../lib/main.css' rel='stylesheet' />
<script src='../lib/main.js'></script>
<script>

  document.addEventListener('DOMContentLoaded', function() {
    var calendarEl = document.getElementById('calendar');

    var calendar = new FullCalendar.Calendar(calendarEl, {

      headerToolbar: {
        left: 'prev,next today',
        center: 'title',
        right: 'dayGridMonth,listYear'
      },

      navLinks: true, // can click day/week names to navigate views
      selectable: true,
      selectMirror: true,

      

      select: function(arg) {
        var title = prompt('Event Title:');
        if (title) {
          calendar.addEvent({
            title: title,
            start: arg.start,
            end: arg.end,
            allDay: arg.allDay
          })
        }
        calendar.unselect()
      },

      

      displayEventTime: false, // don't show the time column in list view

      // THIS KEY WON'T WORK IN PRODUCTION!!!
      // To make your own Google API key, follow the directions here:
      // http://fullcalendar.io/docs/google_calendar/
      googleCalendarApiKey: 'apiキー',

      // US Holidays
      events: 'googlecalendar id',

      eventClick: function(arg) {
        // opens events in a popup window
        window.open(arg.event.url, 'google-calendar-event', 'width=700,height=600');

        arg.jsEvent.preventDefault() // don't navigate in main tab

        if (confirm('Are you sure you want to delete this event?')) {
          arg.event.remove()
        }
      },
      editable: true,
      dayMaxEvents: true,
      

      

      loading: function(bool) {
        document.getElementById('loading').style.display =
          bool ? 'block' : 'none';
      }

      

    });

    calendar.render();
  });

</script>
<style>

  body {
    margin: 40px 10px;
    padding: 0;
    font-family: Arial, Helvetica Neue, Helvetica, sans-serif;
    font-size: 14px;
  }

  #loading {
    display: none;
    position: absolute;
    top: 10px;
    right: 10px;
  }

  #calendar {
    max-width: 1100px;
    margin: 0 auto;
  }

</style>
</head>
<body>

  <div id='loading'>loading...</div>

  <div id='calendar'></div>

  <form action="logout.php" method="POST">
   <input type="submit" name="logout" value="ログアウト">
   </form>
</body>
</html>