The preview could not load.. X to Pro, Up to date

[kturnwald]

So after a few months of troubleshooting and testing I am still the getting “The preview could not load. This is most often related to a plugin conflict or aggressive page caching…” error.
This site started as X with cornerstone, didn’t have any issues until updating X and cornerstone. Since then through testing I have migrated the site to Pro and updated wordpress. X and cornerstone has since been removed from the site.
Before and after migrating to Pro I am getting the error on the home page editor and when going to theme options. Editing the rest of the pages of site is still functioning, no error.
I read the related topics here and have done the basic troubleshooting that is provided in most of those topics.

1. Up to date 2.5.5 Pro, 5.1.1 Wordpress, php 7.1.26
2. Disabled all plugins, same error.
3. Php memory limit increased to 512M

Other troubleshooting- Migrated the site to a new server for testing no error. So I did a wipe of the current server to see if that resolved the issue, no luck so now I am here. This told me that it is definitely a server side issue just unsure what it is. Two different hosts, could this clients host not be enough to run it? Are they holding back the memory limit even though I set it to 512M?

Thanks in advance I tried to do my due diligence before posting!

[friech]

Hi @kturnwald,

Thank you for writing in, you mentioned getting the error on the home page and theme options, but not on other pages

Please contact your hosting support and ask to deactivate the ModSecurity (or any other security feature), then check your homepage in Cornerstone to see if that resolves the issue. If it does, since deactivating ModSecurity is not recommended, request to enable it back and unblock/whitelist only the pro directory \wp-content\themes\pro\*

Let us know how it goes,
Cheers!

[kturnwald]

That did the trick! Thank you for the quick response and solution!

[friech]

We are delighted to assist you with this.

Cheers!