Thanks for writing in and sorry to hear that your having an issue.
The first thing we check this case is the license. I see that you only have a Cornerstone license so I wonder if you’re validating X Theme or Cornerstone. If you have X theme in your site, please register the license here in Apex first then you can retry the Product Validation.
If you’re validating Cornerstone, please try or confirm that you have tried all the suggestions in our Troubleshooting - Validation Connection Issues article. Connection problems are usually caused by a security configuration or a lack of feature in the web host’s side. If you can, I’d also recommend that you try other web host for testing.