Found the solution in the documentation! Thanks!
Example1: I have had many clients who complained about the WordPress Simple Shopping Cart’s variation not working properly on their site. After I finished my troubleshooting, it turned out that the theme was missing the following piece of code in its footer file (footer.php)!
<?php wp_footer(); ?>
This piece of code tells WordPress to add certain bit of code to go in the footer of the page (e.g. load a JavaScript file). So any plugin that tells WordPress to do some stuff in the footer will not work because the above code is missing from the theme.
