Thank you for writing in, first please navigate to your Licenses page and assign your site URL to your license. Right now I don't see any URL that is assigned to your license.
After that, please try to validate your site again.
If the issue persists, usually the cause of this issue is not a compatible version of X and Cornerstone, in this case, you need to make sure that both X and Cornerstone are up to date, you can compare your version to what is the latest version in here.
Updating Your Themes and Plugins
You might need to follow the Manual X Update Via FTP guide from that article since the Automatic Updates will not work in this case as your site is not validated.
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.
Hope it helps,