I tried it with your code and it still doesn't work (doesn't require any input into the text field, let alone the correct one).
When I follow the Getting Started Guide I end up with this:
$WAFV_Errors .= WAValidateLE(strtolower($_SESSION['captcha_Security_Code_1']) . "",strtolower(((isset($_POST["Security_Code_1"]))?$_POST["Security_Code_1"]:"")) . "",true,1);
I've started over quite a few times and always end up with this. But it doesn't work either.