recaptcha not work Joomla! 3.6.5

[2dmaster]

why recaptcha not works on joomla 3.6.5 ?

JHtml::_('behavior.keepalive');
JHtml::_('behavior.formvalidation');
$user=JFactory::getUser();
if($user->guest){
JPluginHelper::importPlugin('captcha');
$dispatcher = JDispatcher::getInstance();
                    $captcha = JCaptcha::getInstance('recaptcha');
             
$dispatcher->trigger('onInit','dynamic_recaptcha_1'); }

<div class="control-group"><div class="controls"><div id="dynamic_recaptcha_1"></div></div></div>
                <div>
                    <button type="submit" class="validate"> <?php echo JText::_('JREGISTER');?> </button>
                    <input type="hidden" name="option" value="com_users" />
               <input type="hidden" name="task" value="registration.register" />
                    <?php echo JHtml::_('form.token'); $html = $captcha->display(null, 'dynamic_recaptcha_1', 'required'); ?>
                </div>

[jenkinhill]

Are you usng Recaptcha 2?