Some block styles not loading in 6.3.1

[mmcalister]

On some new WordPress installs with block themes, core styles for the navigation and other blocks are not loading.

This is happening on some fresh installs on live sites (screenshot above is from a fresh InstaWP install), but I can't replicate on local dev environments.

A friend initially reached out with this error a few days ago on his site using TwentyTwentyTwo. After troubleshooting for hours, I had no fix for it. Then, last night, I saw this same issue with my own theme on an entirely different server.

When I switch back to 6.3, this issue is not present.

This is a hard one to reproduce, but you can see live on this temporary theme demo: ​https://eeable-ape-xaho.instawp.xyz/. If you want to create a site and experience the issue live, go to this theme demo site and create an admin theme demo: ​https://demo.olliewp.com/live-demo/

Go through the setup wizard and click through the steps to create some pages. You'll be able to see the issue at the end of the wizard when you view the site.

[mmcalister]

Preview of the issue

[mmcalister]

Preview of the issue

[joemcgill]

Hi @mmcalister and welcome to Trac! I suspect you're running into the same issue described in #59111, though the version difference from 6.3.0 to 6.3.1 is a new detail. Would you mind trying to add the following line to the wp-config.php file for that site and see if your problem goes away?

define( 'WP_DEVELOPMENT_MODE', 'core' );

[mmcalister]

Hi @joemcgill. Thanks for the quick response! That did indeed fix the issue on that site. As you can see, the site appears as it should now: ​https://eeable-ape-xaho.instawp.xyz/

Looks like this may be a duplicate of that existing issue. If so, we can close this up. Thanks again!

[joemcgill]

Duplicate of #59111.

Thanks for confirming! I'm going to close this as duplicate and add your specific details to the other ticket so we can make sure we account for your use case in the eventual fix. Feel free to participate in the conversation in that ticket.