The preview could not open due to iframe response being incomplete

I have tried:
Updated Theme
Updated PHP
Disabled all plugins
Deleted Cache, both locally and server

Nothing solved the problem. Can someone help?

1 Like

Nobody? I can’t upload anything on the website

Downgraded Theme
Downgraded Wordpress
Downgraded PhP
Deactivated Plugins
Installed New copy of Wordpress
Nothing seems to solve it

@ruenel can you please help me out?

Posted this two days ago, can someone get back to me, even with some acknowledgment that it has been seen?

Hello Alexandru,

Thanks for writing in!

Just for future topics, self responding or bumping your post pushes it back in our Queue system so it takes longer to respond to. We provide support to our customers 24/7/365 in the Support Forum. Support questions are answered in the order received and responses may take up to 24 hours (typically sooner). Complex questions or busy times may take longer.

Since you have already done troubleshooting the most common issues, kindly provide us access to your site so that we can check your settings. Please create a secure note with the following info:
– Link to your site
– WP login URL
– WP username
– WP password
– WP Administrator Role
- Confirmation that we can access and make changes to your site

To know how to create a secure note, please check this out: How The Forum Works

Best Regards.

I apologize, didn’t know that.
Secure Note added, thank you!

Hello Alexandru,

Please go to Tools > Site Health. Kindly resolve the performance issues.
Use PHP 7.4. If nothing is working, please re-install the Pro theme:

Kindly let us know how it goes.

Hi @ruenel,
As I mentioned above I have updated everything, however had to downgrade some because different issues with plugins.
For the sake of solving this problem which is so frustrating,
I’ve have just tried the following:

  1. I updated PHP to 7.4
  2. Deleted inactive plugins
  3. Deleted inactive themes
  4. Reinstalled PRO 4.2.3
  5. Cleared browser and server cache

The issue still persists. I have no idea what is going wrong. All of the other websites running on same server with Pro theme are working just fine.

Hi Alexandru,

Unfortunately, I am not able to log in to your website and it shows a Too Many Redirection error.

Can you please check once, and let us know once it ready to access. I would also suggest you go through the common issue troubleshoot to recognize your problem.

1.Plugin Conflict
2.Theme Update related issue
3.Child Theme Related issue
4.CSS/JS Customization
5.Disabling Cache

If you discover that an issue is coming from a custom code or 3rd party plugin, kindly consult with a developer or contact the plugin author. Please note that we do not provide support for custom codes and 3rd party plugins.


The website is working and it worked based on the analytics, please make sure you delete your cache.

Of course the issue is still there, please look into it.

I also tried to roll my website to the backup I had made before this issue, but the issue is still there.

Hi Alexandru,

I can’t access your website, it seems that it is down. Please contact your hosting provider for further assistance.

Thank you.

Hi @marc_a
I am not sure why the website doesn’t work for you guys, since I tried everything after you guys said is not working and it always did work.
On top of that I check GA and I have 8-10 users in real time all the time. Try www and non www as well, shouldn’t make a difference though.

Hey Alex,

The message in the console points to Cloudflare. Would you mind disconnecting your site from Cloudflare temporarily to test if it’s causing the issue?


Cloudflare deactivated, issue is still there.

Hi @al2code,

I’ve checked your site and have some more information about what is going on here. Anytime WordPress finishes running a request, it fires a hook called shutdown. This should always happen after the closing HTML tag. When the preview frame loads, we output a signal that looks like CORNERSTONE_FRAME to indicate that the preview reached the end without any unexpected failures. Our system expects to see this:


On your site, it looks like this:

CORNERSTONE_FRAME<script type='text/javascript' style='display:none;' async>

<script type="text/javascript" data-cfasync="false"></script></body></html>

Something on your server is rewriting the HTML, and it confuses the builder live preview. That extra code doesn’t seem to do anything either. I tried some testing with plugins off as well and had the same results. Oddly, that code doesn’t seem to even do anything at all so I’m not sure why it would be added.

Are you aware of anything on the server that could be rewriting the HTML? If not, from here I would recommend checking with your host to see if they can uncover why that is outputting.

I see, thank you for looking into it, unfortunately I don’t know anything that can cause the issue, the website was working perfectly and suddenly it stopped.
To be honest I am not sure what to do next, since I tried everything. What can rewrite HTML?

This is how my .htaccess looks like.

BEGIN WordPress

The directives (lines) between “BEGIN WordPress” and “END WordPress” are

dynamically generated, and should only be modified via WordPress filters.

Any changes to the directives between these markers will be overwritten.

RewriteEngine On RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}] RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L]

END WordPress