Theme Pro Cornerstone Builder preview error


We are having an issue with the page builder preview and receiving the “The preview could not load due to the iframe response being incomplete…” error. The preview error only happens when pages are ‘published’ or ‘private published’, and preview functionality will return if pages are set and saved to ‘draft.’ Also note that there is an exception to this with our homepage, with this page functioning as expected regardless of the pushing status.

We have already gone through and disabled all plugins, as well as our child theme to see if the issue could be coming from there, however, the issue persists in all cases. We have tried to identify any common components or global blocks that could be contributing to this across the pages that are giving us the errors but are unable to find anything. We have also come across other threads where some people are having similar issues however the solutions were not clear.

Please advise on what the next steps will be how this can be resolved. Thanks for your time.


Hi Kelly,

Thanks for reaching out.
I have checked the website listed in your Themeco Account and found that the staging site is still using the older version of Pro i.e. 5.1.0. If you are having an issue with your staging, please update the Pro and check if that resolves your issue.
If you are having the issue in your live site and already troubleshoot the common issues listed here, it will be very difficult to recognize the issue without investigating through the admin dashboard. Can you please provide login credentials for your site in a secure note to examine it further, including:

– WordPress Site URL & Login URL
– WordPress Admin username/password

To create a secure note, click the key icon underneath any of your posts.


Thank you for the quick reply. That staging instance is currently out of service. We have been able to use the Yoast Rewrite & Replush functionality as a temporary workaround for the issue. I will be setting up a new staging instance that is current with the live site and will advise when that is accessible.


Great! Please let us know if you have the staging site setup already.