Hello @mcphoto,
Thanks for writing in!
It seems that you have updated X theme to version 6.5.6 and yet Cornerstone is still using 1.3.0. Please do the following:
1.) Go to the Plugins section.
2.) Find Cornerstone plugin 1.3.0 and deactivate it.
3.) Delete the Cornerstone plugin.
4.) Go back to X > Validation and wait for a few seconds while Cornerstone is being installed automatically.
5.) If the automatic installation fails, you can get the latest Cornerstone 3.5.5 from the link in the secure note.
By the way, Please be advised that we have just released X 7.0.2 and Cornerstone 4.0.2. It is now available in automatic updates. You can now update to this latest version. This latest release contains fixes for several issues so be sure to check out the changelog (http://theme.co/changelog/).
After doing the updates, always remember to clear all caches (if you are using WP Rocket, WP SuperCache or W3 Total Cache) when updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
Regards.