You do not have to purchase another license if you have changed your domain.
You just need to update the URL set to the license in the licenses page then go on with the validation.
As for the issue in Cornerstone, please make sure to check for the following first:
- We'd recommend that you increase your memory allocated to PHP if you haven't done so already. To increase it, please edit your wp-config.php file and insert these lines:
define( 'WP_MEMORY_LIMIT', '256M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
If the issue is still there, please make sure that you have everything updated to the latest version especially for X and Cornerstone. You can find more info about the support versions of X and its bundled plugins here.
If you are still seeing an issue, please try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Let us know how it goes!