If you have tried to optimize the speed of your WordPress site with your own hands, then the following problem most likely also occurred to you.
The bottom line is the message that appears: “This theme is corrupted. Template is missing. Standalone themes need to have a index.php template file. Child themes need to have a Template header in the style.css stylesheet.”
You will see a similar message on the “Site Health” page, as well as directly on the “Themes” tab.
The problem is simple, but unsettling. Understanding.
First, since you’ve got such a nice error, you definitely have a child theme installed. This is doubly good because child themes are correct and because the problem is not difficult to fix.
Secondly, despite the damage to the theme, the site continues to work…
This happens most often when you’ve compressed (edited, optimized) the child theme’s style.css file. At the beginning of this file there is an “unnecessary” comment describing the topic. So that’s exactly what you deleted. It is only necessary to return it to its place 🙂
You can restore the “labels” of the style file from a backup (server or WordPress), but it takes a long time.
The easiest way is to create a new child theme using the Child Theme Configurator plugin, and then transfer the necessary files from the broken theme folder to the new theme folder. To do this, you can use any file manager, for example WP File Manager.
Although you can cheat a little and instead of transferring files from the old (but so familiar) theme to the new one, take and rearrange the missing introduction to the old style.css file 🙂