Please make sure that you are validating through X > Validate in the admin section and not the Cornerstone validation.
To verify this, if you are seeing this in the admin,
then you will have to make sure that X is activated on your site then validate it.
Please also try deactivating all the plugins when validating.
If you already have X active, please post the license key in a Secure Note that you are using so that we can check.