Thanks for writing in. It sounds like you're having a connection issue because if you're still using the same domain you've assigned to your license, you should be able to validate.
Have you gone through the Troubleshooting - Validation Connection Issues article. If not, please try the solutions suggested in the article. Usually, it's the cURL setup of the web host that is causing the issue. We have a sample letter in the article that you could use to ask your web host.
Also ensure you have not assigned your domain to both the Production and Staging fields.
If you've tried every suggestion in the article and nothing helps, please give us WordPress Admin username and password and FTP username and password in a Secure Note. Also post your license key still in the Secure Note so we could test validating your site.