Hello,
I see a lot of people have the same issue. I on a fresh install. No plugins activated, no caching no cloudflare. I try to edit the example page of wordpress fresh install and I get the error:
A conflict on the front end of your site has prevented the preview from loading.
I removed the theme, downloaded again and installed but the problem remains. The website is part of multisite network using https. Waiting for your help. Thank you!
I see that if I use your theme for the main site of multisite network cornerstone works, but if I use it for other website moving licence (clean install, same environment) in does not work.