Hello Mel,
Thanks for writing in! To be able to validate your X theme in your site, 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/ format. Please 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 Addons > Product validation, and insert the license code.
For further information about product validation, please check out our knowledge base
https://community.theme.co/kb/product-validation/
Hope this helps. Kindly let us know.