[Plugin Captcha] The use of the captcha on custom form doesn't work

Hello i’m using the Captcha plugin but i’m having a small issue!!! I have added the code that is required in order to work but i’m having a problem that the Captcha is not been refresh if the user doesn’t input it or put it wrong. How i can make it to be refresh and show an error message if the user enters a wrong number?

I have added this in my custom login page which it is works with Ajax

<p class=”form-cptchleft”><?php if( function_exists( ‘cptch_check_custom_form’ ) && cptch_check_custom_form() !== true ) echo “Please complete the CAPTCHA.” ?></p>
<p class=”form-cptchright”><?php if( function_exists( ‘cptch_display_captcha_custom’ ) ) { echo “<input type=’hidden’ name=’cntctfrm_contact_action’ value=’true’ />”; echo cptch_display_captcha_custom(); } ?></p>

and this is when the user press the login button
elseif (cptch_check_custom_form() !== true)
{

}

what action i have to add in the elseif to refresh the captch?
Thank you