Warnings in the Builders

In this article, we're going to explain common causes of the builder warnings in the X, Pro and standalone Cornerstone plugin and the troubleshooting methods

  1. Origin Url and Preview Url
  2. Preview Loading Error Messages
  3. Other Errors
  4. How to Test for a Plugin Conflict
  5. SiteGround Staging Issues
  6. Summary

Origin Url and Preview Url

If you encounter a preview error in the builder and the message shows you the original and preview URLs, check to see if the domain of the two URLs is the same. The original URL is where you view the application, and the preview URL is where the builder tries to load the preview panel and it uses the home_url WordPress function.

The bottom line is that you need o make sure that the main domain section of the original and preview URLs are the same to make sure that preview will show correctly.

Preview Loading Error Messages

You may encounter different cases when it comes to the preview loading errors. We will discuss each of these cases in detail.

A conflict on the front end of your site has prevented the preview from loading.

The error above is the placeholder error for all the problems that might occur regarding the preview of the builder in the old versions of X, Pro, and the standalone Cornerstone plugin. Update X, Pro, and the Cornerstone to the latest version to have a more descriptive error instead of this one.

The preview could not load due to a http/https mismatch. Please check that HTTPS is properly configured on your site.

If you check the website with http but the builder tries to retrieve the preview using https this error might happen. The troubleshooting steps for this case are as follows:

  • Make sure that if you have HTTPS enabled that you are working in the builder over HTTPS as well.
  • Try deactivating any HTTPS related plugins you have installed
  • Under Settings > General in your dashboard, make sure both the WordPress and Site URL share the same protocol.
  • Consider forcing HTTPS everywhere. If you have the ability to run HTTPS, nowadays it's just better to use it exclusively. Google claims this will even result in higher indexing.
  • Contact your hosting service provider and ask them for help regarding the case.

The preview could not load due to misconfigured URLs. This could happen if you are using multiple environments and the site URL was not updated after migrating.

If you use a staging environment, it might be the case that you migrated the database but the base URLs are not changed in the database for some reason. Some hosting service providers provide staging tools that might have the same issue. Follow the steps below for troubleshooting:

  • Check Settings > General in your dashboard. The WordPress URL and Site URL should match the domain in your address bar.
  • Contact your hosting service provider and ask them to check if the base URLs are updated correctly or not.
  • There is a known conflict with SiteGround staging environments. Their staging provisioner relies on Apache URL rewriting. WordPress is still using the production URL internally, so the staging site doesn't really know it's a staging site. There are situations where plugin and theme logic (including Pro and Cornerstone) may end up using URLs from the production site because the staging system can't account for rewriting URLs in every context they may be used.

The preview could not load due to the iframe response being incomplete. This is most often related to a plugin conflict, or customizations introducing a PHP error.

The error above shows that there is a fatal PHP error which stopped the rendering of the website and you need to follow the steps below:

  • Enable the WordPress debug mode. You might be able to see an error message on the site right away. If not, the error log could reveal where the problem is originating.
  • If you're using a child theme, try switching to the parent theme to see if that makes a difference. The conflict could be in your customizations.
  • Test for a plugin conflict by disabling all third party plugins except the Cornerstone plugin if you use X. IF the problem is fixed, activate the plugins one by one to find the plugin responsible for the problem.
  • Make sure that you use PHP version 5.6.x or 7.1.x or 7.2.x. Contact your hosting service provider to make sure that you do not have an old version of the PHP.
  • Make sure that you increase the PHP memory limit to at least 512M. Follow the steps mentioned here for more information.

The preview was unresponsive after loading. This is most often related to a plugin conflict or aggressive page cacheing.

This is happening mostly because of the heavy caching on your website. Follow the steps below:

  • Clear any caches. An older version of the page could be stored, preventing the builder from loading
  • Test for a plugin conflict as mentioned above.
  • If you're using a child theme, try switching to the parent theme to see if that makes a difference. The conflict could be in your customizations.
  • If you are using a CDN system, try to disable it temporarily and check the case.

The preview could not load. This is most often related to a plugin conflict or aggressive page cacheing. Checking the developer console for errors could indicate what went wrong.

The errors above are the most common and the cause of the problem is unknown. You can check the developer console of your browser to see if you can find any specific errors. If you need any further help, you can reach the team directly in our forum.

Other Errors

The preview HTML did not include a closing; tag. It may fail to load or work properly.

This is the red error message that appears and indicated that there is a fatal PHP error. It is usually happening due to the plugin conflicts.

How to Test for a Plugin Conflict

With many of these problems being related to plugins, testing for a conflict is often the fastest way to get to the bottom of things. Here's a simple plugin conflict testing process:

  • Disable all plugins except Cornerstone. If you're using Pro, disable all plugins.
  • Test to see if the issue remains.
  • If things are working again, reactivate one of your plugins
  • Test to see when the problem reappears
  • If it does, you know the plugin you most recently activated is causing a problem. If it doesn't, go reactivate another plugin.

SiteGround Staging Issues

There's a known issue with SiteGround staging environments where the builder tries to preview on the production URL. It happens because to make DB updates go smoother, SiteGround doesn't update the site URL inside WordPress, instead, they rewrite it as the site is rendered. This has a side effect of any plugin/theme that uses the site URL directly from the database could end up using the production version instead. SiteGround is aware of this, and they've informed us they're working on improvements to their staging system to account for the additional cases.

To fix the issue, they are recommending that you change the URLs before and after deploying. Here's a guide for that process:

  1. After creating your staging environment, go to Settings > General in your dashboard. Update the WordPress and site URLs to match the staging URL. For example staging-1-2-3.yourdomain.com
  2. Work on your site as usual.
  3. Before redeploying to production, go back and return the URLs to the production URL. If you fail to set the URL back before deploying, it will break the URLs on the production site.


We've looked at different possible errors that you may encounter while trying to preview the website in the builder and discussed the common troubleshooting steps you can take. If you're still having difficulties, reach out in our forum, and a member of the team will be happy to assist.

See something inaccurate? Let us know