i m trying to send fax with plain text and pdf in sand box mode , but still i received partially fax and without any attachment or fax text ..

require(APPPATH.'libraries/ringcentral-php/vendor/autoload.php');

$rcsdk = new RingCentralSDKSDK(CLIENTID, SECERTID, RingCentralSDKSDK::SERVER_SANDBOX);

$platform = $rcsdk->platform();

$response = $platform->login(USERNAME, EXTENSIONID, PASSWORD);

$request = $rcsdk->createMultipartBuilder()

->setBody(array(

'to' => array(

array('phoneNumber' => '(888) 908-7116'),

),

'faxResolution' => 'High',

))

->add('Plain Text', FCPATH.'faxdata/test.txt')

->add(fopen('https://medicalprior.serverhtf5.info//faxdata/test.txt', 'r'))

->request('/account/~/extension/~/fax');

$response = $platform->sendRequest($request);

print 'Sent Fax ' . $response->json()->uri . PHP_EOL;
...........................................
file Path is correct i double checked ...
my text file in just kb , it s not tooo long or more than 1mb

??????
this is received fax
+14244274896-1009-153548-079.pdf