It seems the problem was related to a missing or invalid User Agent.
It can be configured in php.ini (In ExeOutput for PHP 1.7 -> PHP Settings tab -> PHP.ini)
Example: user_agent="Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0)"
or
using cURL
Example: curl_setopt($ch, CURLOPT_USERAGENT, ‘Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0’);