使用battlefieldtracker.com的API

I'm trying to use the API of battlefieldtracker.com. There is a docu under: http://docs.trnbattlefield.apiary.io

At first I generated an API-key. My second step was to use the documentation to generate the request:

<?php
$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, "https://battlefieldtracker.com/bf1/api/Stats/DetailedStats?platform=3&displayName=PENTA-piidde&game=tunguska");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_HEADER, FALSE);

curl_setopt($ch, CURLOPT_HTTPHEADER, array(
  "TRN-Api-Key: xxxxxx-yyyyyy-aaaaaa-bbbbb-ccccc"
));

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

var_dump($response);

The result in PHP is:

bool(false)

In the online try-area of the documentation is my result in any case:

501

    Headers
    server:Cowboy
    connection:keep-alive
    x-newrelic-app-data:PxQDVFVRCQITVlZRDgcFV0YdFGQHBDcQUQxLA1tMXV1dSnwZQRNWERdcRE4hJmwcH05DThoBGVZUABoDTFZVWgBQAVsIChgCH0cIVAdUClQAUlMCVVZbBgBGTQRWXUQDOQ==
    access-control-allow-origin:*
    access-control-allow-methods:OPTIONS,GET,HEAD,POST,PUT,DELETE,TRACE,CONNECT
    access-control-max-age:10
    x-apiary-transaction-id:5908b3c55e9e851900cf77f1
    content-length:0
    date:Tue, 02 May 2017 16:28:53 GMT
    via:1.1 vegur

Does anyone have an idea to share?