Not able to see successful popup message while subscribing newsletter on footer

My opencart version is 1.5.6.4. I am using a custom theme(bromic by Kuler theme) for my store. The problem for (registered and unregistered) users
is that after entering email id to subscribe newsletter on footer, My users do not get this message "you have successfully subscribed to our newsletter" and I do not get to see subscriber list on my admin. Instead we get loading sign continuously. For a better view I am attaching a pic. I am also using a newsletter module for my website
I am very new to opencart so if anybody requires any code / file please let me know.

My website url is http://interiomarket.com/

Anyone?

This is what I found out in catalog/view/theme/bromic/template/common/footer.tpl


<?php if ($kuler->getSkinOption('show_newsletter')) { ?>
<div class="col-md-3 col-sm-4 col-xs-12 newsletter wow bounceInRight" data-wow-offset="300">
<?php if ($kuler->getSkinOption('show_newsletter_title')) { ?>
<h3><span><?php echo $kuler->translate($kuler->getSkinOption('newsletter_title')); ?></span></h3>
<?php } ?>
<form id="newsletter-form" action="" method="post">
<?php echo $kuler->translate($kuler->getSkinOption('newsletter_description_text')); ?>
<input type="email" id="newsletter-mail" name="email" placeholder="<?php echo $kuler->translate($kuler->getSkinOption('newsletter_input_text')); ?>"/>
<button id="newsletter-submit"><?php echo $kuler->translate($kuler->getSkinOption('newsletter_button_text')); ?></button>
</form>
<script>
Kuler.show_newsletter = <?php echo json_encode($kuler->getSkinOption('show_newsletter')); ?>;
Kuler.newsletter_subscribe_link = <?php echo json_encode($kuler->getNewsletterSubscribeLink()); ?>;
</script>
</div><newsletter>