Hi Kendall,
You have an outdated version of the X theme (4.6.4) and Cornerstone (1.3.3), the latest version is 6.5.6 and 3.5.5 respectively.
Please follow the Manual Updates guide provide here, follow the Manual Updates since the Automatic Updates likely will not work on your current version. You can download an updated and fresh copy of X in the APEX dashboard here or on your ThemeForest account.
After you successfully updated the X theme, deactivate and delete Cornerstone (1.3.3), then you’ll see a notice on top of your dashboard to install Cornerstone, click that and it will re-install the latest version of Cornerstone.
Remember to clear all your caching features (plugin, server-side, CDN, and browser’s cache) after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
Now try to validate your site again using your license.
Hope it helps,
Cheers!