This error is triggered by corruption in your WordPress database. If you see this error, you’ll likely need to backup your site, delete the corrupted database, and restore it.
This is by no means an exhaustive list of all the errors that can occur when your WordPress theme is not working, but it does cover some of the most common issues. Now that you understand why your WordPress theme might not be working, let’s dive in and look at some of the solutions you can try.