The login credentials is still not working for us.
Anyway, you cannot validate your theme because you haven't assigned the domain in your licenses page. To validate X properly, please do the following:
1] Please login to your account and assign the license (https://theme.co/apex/licenses). You need to assign the license to your site using this url: https://www.example.com/ (Or the URL of you staging site). 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