Issue retrieving contents through Google Cal API - php

Question

Working on a WP plugin. It's end purpose is to serve as an inspection calendar for home inspectors. We're working with a Google Calendar that is already loaded full of events.
I am authenticating via Oauth2 & a Service account. The plugin needs only to access the inspection company's data, no other private user data.
Here's the code:
// Set up identity ------------------------------------.
$client_email = "XXXXXX#XXXXXXXXXX.iam.gserviceaccount.com";
$private_key = file_get_contents( EC_INSPECT_CAL_INC . "/HE_Web_1.p12" );
$scope = [ "https://www.googleapis.com/auth/calendar","https://www.googleapis.com/auth/calendar.readonly","https://www.google.com/calendar/feeds" ];
$credentials = new \Google_Auth_AssertionCredentials(
$client_email,
$scope,
$private_key
);
// Build Config Obj ------------------------------------.
$config = new \Google_Config();
$config->setClassConfig('Google_Cache_File', array('directory' => EC_INSPECT_CAL_INC . '/tmp/cache'));
// Instantiate Client Connection ------------------------.
$client = new \Google_Client( $config );
$client->setAssertionCredentials( $credentials );
if( $client->getAuth()->isAccessTokenExpired() )
$client->getAuth()->refreshTokenWithAssertion();
$service = new \Google_Service_Calendar( $client );
$calendarList = $service->calendarList->listCalendarList();
while( true )
{
foreach( $calendarList->getItems() as $calendarListEntry )
{
// get events
$events = $service->events->listEvents( $calendarListEntry->id );
foreach( $events->getItems() as $event )
echo "-----".$event->getSummary() . "<br>";
}
$pageToken = $calendarList->getNextPageToken();
if( !$pageToken ) break;
$optParams = array('pageToken' => $pageToken);
$calendarList = $service->calendarList->listCalendarList($optParams);
}
}
If I var_dump the following:
var_dump( $service->calendarList->listCalendarList() );
It results in:
array(0) { }
My wife would like me to stop cursing in front of the dogs, but I can't seem to figure out what I'm overlooking. The calendar is loaded with content, and I (AFAIK) am authenticating ... So where's the goods??