Thanks for updating in! Please be advice that an API key has been deprecated. You do not need to use it in the latest version of X. Please download the latest version from your dashboard. You can get it from here: https://theme.co/apex/dashboard
Once you have installed X, you can make use of the license code instead. To validate X properly, please do the following:
1] Please login to your account and assign the license. You need to assign the license to your site using this url: https://www.example.com/. You have to make sure that url you just assign is the same as the one you have in your settings, Settings > General > Site Address
2] Go back to X > Overview again, and insert the license code.
And please review the changes that we made on how you are going to validated your X theme because we made a big change in the process. Please check it out here: https://theme.co/apex/forum/t/setup-product-validation/55