recaptcha working on local but not on live wordpress sites

Hi I have a form I've made that works on my local machine but doesn't run the get_file_contents on the live server as it returns NULL on the response?

Form:

 form name="contactUS" action="?php echo get_template_directory_uri(); ?/mail/contact-us-mail-recaptcha.php" method="post"

input name="name" type="text" placeholder="Name"
input name="email" type="email" placeholder="Email"
input name="message" type="textarea" placeholder="Please describe your project and the work to be done?"
div class="g-recaptcha" data-sitekey="site key"/div
button type="submit" class="nsc-button"Submit/button
/form

Server Code:

?php

$recaptcha_secret = 'secret key';
$ip = $_SERVER['REMOTE_ADDR'];
$captchaResponse = $_POST['g-recaptcha-response'];

$response = file_get_contents("https://www.google.com/recaptcha/api/siteverify?secret=".$recaptcha_secret."response=".$captchaResponse); 

$result = json_decode($response, true);

if($result == true){

//do success
}else {

    var_dump('ip:' . $ip);
    var_dump('captchaResponse:' . $captchaResponse);
    var_dump('response:' . $response);
    var_dump('result:' . $result);
    exit;

}