It doesn’t work.

Please provide a link or I cannot help

Can you please confirm that HD Quiz is active (not just installed, but that you have it active) on your site?

I also see you are using something called Powered Cache. If HD Quiz IS confirmed active, please try clearing your site cache within Powered Cache.

Unfortunately,
All that I can say from this side of your site is if HD Quiz is loaded, then only two possible things can happen with the shortcode. Either the quiz displays, or you get a message “Quiz not found”.

Since your site is showing the shortcode text instead of displaying anything, this means that either HD Quiz is not active on your site, or is otherwise being prevented from loading by something else on your site.

You can attempt the default WordPress debug steps of disabling all plugins except HD Quiz to see if that works. If it does work, we know the issue is caused by another plugin and you can re-enable each plugin one by one to find the culprit.

It is also always safe to downgrade versions of HD Quiz.

You can down the previous version here at WordPress. The version you want is 1.8.15.

And lastly, only if you are comfortable with it, you can contact me using the form on harmonicdesign.ca to provide me with login access to your site. I can take a look to see if I can see what’s wrong with your site.