your page does not have enough to test whether captcha is working or not
add the following code after the body tag to show a message if the form posts succesfully:
<?php if($_SERVER['REQUEST_METHOD'[ == "POST") { ?>
The Form Posted Succesffuly.
<?php } ?>
the captcha error is stored in a session that will only be cleared if the form posts successfully, you can manually clear the session by adding this code after the </html> tag:
<?php if(isset($_SESSION['captcha_Security_Code_1'])) unset($_SESSION['captcha_Security_Code_1']); ?>