Thanks for writing in! It seems that you are using a quite older version if X. API has been replaced with license code way back in X 4.x. Because of this, you will have to manually update X.
Our latest versions are:
X Theme: 5.1.0
You can find the latest version numbers here: (http://theme.co/changelog/) Then you can compare them to what’s installed on your site.
If you find anything to be out of date, you can review our update guide.
After updating,please make sure that X is validated. Please check out the new way of validating X;
Hope this helps. Please let us know how it goes.