PayPal Express Checkout won't redirect to Paypal.com

Question

This is my website: http://boostingfactory.com/heroes-of-the-storm/rank-boost/

Test a random checkout and you'll see it just won't redirect to Paypal.com

I actually talked to their Technical support they told me that the module successfully requests a token but just doesn't redirect to the payment on paypal.com for some reason.

This is the module: http://pastebin.com/wbgTs35b

What do you think could be causing this?

This line particularly:

function RedirectToPayPal ( $token ) { 
  global $PAYPAL_URL;
  $payPalURL = $PAYPAL_URL . $token; 
  header("Location: ".$payPalURL); 
}