Google calendar entries not displaying

I'm having the same issue. Added my API key and Google calendar ID in to the calendar, and nothing this displaying.

I managed to make it work by attaching the missing Google Calendar library to my Fullcallendar view in my custom module:

use Drupal\views\ViewExecutable;

/**
* Implements hook_views_pre_render().
*/
function YOURMODULE_views_pre_render(ViewExecutable $view) {
  if (isset($view) && ($view->storage->id() == 'YOURVIEW')) {
    $view->element['#attached']['library'][] = 'fullcalendar/fullcalendar.googlecalendar';
  }
}