Hello Jeremy,
Please also make sure to update the domain name that is associated with the license that you are trying to use to validate. If the domain name is updated but you are still not able to update, please check your X, Cornerstone and Wordpress version and make sure they are all updated and that X and Cornerstone are the most recent version to avoid incompatibility issues.
If the issue persists. 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!