How to get a file from the Zamzar service?

Question

PHP

Hello!
If anyone has come across using api zamzar - www.zamzar.com , so I do everything, I upload the file, everything is in order, but for some reason I can’t download it, according to the official dock:

<?php
$fileID = 3;
$localFilename = '/tmp/portrait.png';
$endpoint = "https://sandbox.zamzar.com/v1/files/$fileID/content";
$apiKey = "f9bddee74";

$ch = curl_init(); // Init curl
curl_setopt($ch, CURLOPT_URL, $endpoint); // API endpoint
curl_setopt($ch, CURLOPT_USERPWD, $apiKey . ":"); // Set the API key as the basic auth username
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);

$fh = fopen($localFilename, "wb");
curl_setopt($ch, CURLOPT_FILE, $fh);

$body = curl_exec($ch);
curl_close($ch);

echo "File downloaded\n";

But for some reason the file is empty. Help what you can)