pdf stay empty with API ... (php)

Hi there.
Can someone help me please ?
My generated PDF only has his own filename into... nothing else...
My HTML file is a full page...
don't understand... ?

<?php
require 'pdfcrowd.php';

try
{
// create an API client instance
$client = new Pdfcrowd("***********", "****************");

$pdf = $client->convertFile('BT1476867149971.html');
$out_file = fopen('BT1476867149971.pdf', "wb");
$client->convertHtml('BT1476867149971.html', $out_file);
fclose($out_file);
}
catch(PdfcrowdException $why)
{
echo "Pdfcrowd Error: " . $why;
}
?>

Hello,

Please send us BT1476867149971.html to support@pdfcrowd.com and we will look into it.