Hi aswiniravella,
I took a look and the issue is how you are loading jQuery. This not only broke HD Quiz, but many other plugins on your site as well.
Take a look at this screenshot of your site: https://imgur.com/Itwjtnw. 19 critcal errors – most of them related to being unable to use jQuery.
The following may not make sense, but I’ll do my best to explain.
WordPress comes with jQuery built right in! Plugin developers load up our own script files by calling WordPress’ jQuery file, linking them together in an isolated environment. This is what stops plugin scripts from having compatibility issues with each other and is a crucial feature of WordPress that stops problems like those that you are right now.
The problem is that you have replaced the native version of jQuery bundled with WordPress and are loading directly from a Google controlled CDN (content delivery network) https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js
. Loading jQuery in this way completely breaks the way that most plugins initialize jQuery. This is beaking your slider plugin, your email subscriber plugin, your tab ticker plugin, and is even breaking core WordPress embed functionality.
HOW TO FIX?
I don’t know how you are loading jQuery on your site, but I assume you are using some plugin to “upgrade” the jQuery version. Disable this plugin, or otherwise, find out what is causing your site to load from the CDN instead of default WordPress to fix.