Google API My Business + PHP + Laravel - class not found

I use OAuth 2.0 flow + google-api-php-client + Mybusiness PHP Classes, but I got errors 'class not found', see below:

use App\Vendors\Google_Service_MyBusiness as MyBusiness;
....

$gClient->setAccessToken($access_token);
$oauth2 = new \Google_Service_Oauth2($gClient);
$userInfo = $oauth2->userinfo->get();
print_r($userInfo); //Works!

$mybusinessService = new MyBusiness($gClient);

//return Class 'Google_Service_MyBusiness_Location' not found:
$mybusinessService->accounts->get('accounts/xxxxxxxx');

//return 'Google_Service_MyBusiness_ListAccountsResponse' not found:
$accounts = $mybusinessService->accounts;
$accountsList = $accounts->listAccounts()->getAccounts();

Full error:

Class 'Google_Service_MyBusiness_Account' not found in file /vendor/google/apiclient/src/Google/Http/REST.php on line 128

Class MyBusiness added in autoload:

"autoload" : {
    "files": [
        "app/Vendors/MyBusiness.php"
    ]
}

All required clsses (eg. Google_Service_MyBusiness_ListAccountsResponse, Google_Service_MyBusiness_Location are in app/Vendors/MyBusiness.php)

What is wrong with my code?

via Chebli Mohamed