Preview could not load in Cornerstone

I’m getting the following error on multiple X Theme sites after the recent updates:

“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.”

I’ve tried the following:

  • deactivating all plugins
  • increasing site memory
  • clearing the cache (only one of the sites has a cacheing plugin, the other does not)
  • deleting Cornerstone and then Validating the sites

I am running the current versions of X theme and Cornerstone.

Please help.


Hey @NoQuarter4U,

Are they all hosted in the same server / web host? If so, your host might have server side cache which has not been cleared. Please contact your host if they have server side caching.

Please also give us WordPress Admin and FTP access to 1 of your sites which does not have caching setup so we could check what’s going on. Kindly post it in a Secure Note.


Please give us the htaccess and FTP credentials also.


Hello @NoQuarter4U,

We have tried to log in your site using the given details. The FTP details does not work for us.
And we still cannot get pass this login form:

Could you please provide the details as well?


Login details have been updated in the secure note.

I have a button in the top bar using shortcode. It has stopped working all of a sudden as well. I haven’t changed anything, so I’m not sure how that could have happened.


I would like to check further but the FTP login credentials provided doesn’t seem to work.

Do you have any IP restriction set in your server?

Please disable it temporarily so we can check.


I’ve provided new login details in the secure note. Let me know if that works.


I’m sorry but it still doesn’t work. Would you mind giving us cPanel access instead? I logged in to your WordPress Admin and checked a page in Cornerstone and in the console, I see that there’s an Internal Server Error. That is a generic error though so we would need server access so maybe we could trace where the error’s coming from.


Information provided in secure note.

Hi @NoQuarter4U,

It’s due to redirect and I can’t find which one is doing it (not with the plugins). It could be your host or URL forwarding setup, do you have any of those? You could try disabling it.

OR, you can try testing it in the different host environment.

All the requests are redirected back to the home page, and that’s what happens when the builder requests a preview. I served the unmodified home page (no cornerstone placeholder). Please check the secure note for an example.


When I visited the sites you linked to in the secure note, there was no redirect to the home page.

I sent your comments to the hosting company and this is the response I got:

Hello David,

Neither of the two examples you gave at the end here return to the home page as shown in the linked screenshots below. There are no redirects in place in your hosting panel, you can see these in the cPanel area under redirects. The only other place a server related redirect would be is in the site’s .htaccess file. The .htaccess file for has none. I’ve also looked at the .htaccess file for the main webroot in public_html as this can, in rare cases, effect the sites created under it and there are not redirects there either other than the baisc mod_rewrite. It does also note that you have w3TC browser cache plugin installed either of these things could be related to your overall issue. It is also possible that this could be a database redirect as noted here ( From everything we can see on this end, the issue is most likely not related to any server specific settings. Please let us know if we can be of further assistance.

The issue arose after a recent theme and cornerstone update. Only one of the sites uses a cache. Any other ideas as to what could be going on?

Hey @NoQuarter4U,

I’m not sure about the redirect that @Rad mentioned because those URLs doesn’t redirect to the home page also. And, only your home page has the issue. I could open the rest of your pages in Cornerstone and they work fine.

I get this 500 error in the console when viewing your frontpage in Cornerstone. Your host will be able to help you trace this error. We understand that this happened after the update but this issue is also connected to your web host. I tried creating a new page and set it as your frontpage but the issue still persist.

There might have been some server security rules, most probably in ModSecurity, that prevents the home page from being opened in Cornerstone.

Would you mind trying completely uninstalling W3 Total Cache first? You have uninstalled it under Plugins but it needs complete removal because it leaves a wp-config setting, htaccess rules and files and folders.

Regarding the issue, the Topbar really does not support shortcodes. You probably have copied an old code which does not work anymore or inserted a custom code in your child theme’s functions.php and switched to the parent theme.

If you have other issues, please open a separate thread for each in order to avoid confusion and it will also help us focus on one issue at a time.


Thanks for taking a look.

The topbar shortcode was working fine until about the same time that this new cornerstone preview issue arose. I can live without it. I just thought the issues might be related due to the issues arising around the same time.

I have uninstalled all cache plugins. I am in the process of trying to delete all left over files and information from W3 cache. I understand that they sometimes leave trailing issues after the uninstall. However, I don’t currently have, and don’t believe that I ever have had a cache plugin installed on the website, yet I have the same problem.

Given that the doesn’t have the same cacheing plugin issues, but has the exact same cornerstone preview issue, can’t we rule out the cacheing plugins as the potential culprit?

Please help.

My web host has resolved the issue. Here is what they said:

“It appears that the theme was raising false positives on the web application firewall and thus being blocked. To test this, we made a couple of adjustments to the web application firewall to allow the theme to execute without blocking it, which seemed to have worked. Please let us know if there’s anything else we can assist you with.”

Thanks for your help.

Glad to hear everything is working fine now.

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