Hello There,
Thanks for writing in!
The api key is no longer required if you are using the latest version of X. This was mentioned in our changelog here (https://theme.co/changelog/#theme-4-4-0). If you are still using the old version of X (4.3) or below, 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.your-domain.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] Please take note of the license code.
2] Go back to X Addons > Product validation, and insert the license code in the api key field.
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://community.theme.co/kb/product-validation/