Hi James,
Were you having issues with the shortcode before you updating X and Cornerstone to the most recent version? Although ideally we would want all the third party plugins to work instantly with X and Cornerstone, there are instances that when a third party plugin is not well coded, it would cause a conflict with the theme and considering the number of plugins available, it goes beyond our capacity to check for their compatibility with X and CS.
X and CS are coded according to Wordpress standard so in most cases, plugin would work fine. However, since this is not working on your setup, we could have a look and see if it’s something we could provided some assistance. Kindly provide us with the admin and FTP details of your site in a Secure Note.
With that being said, it would still be best to get in touch with the plugin developer and see what advice they can provide as well.
Kindly also check that you are update to the latest version of X and CS.
https://theme.co/changelog/
Thank you.