In this post, we covered a wide range of possible causes and fixes for this issue. Let’s recap them quickly:

1. Restore a previous version of your site.
2. Disable all of your plugins.
3. Activate a default theme.
4. Make sure you’re an administrator.
5. Check your error log to pinpoint the cause.
6. Ensure that your database prefix is correct.
7. Look for changes in your wp-config.php file.
8. Upgrade to the latest version of php.
9. Evaluate your file permissions.
10. Create a new .htaccess file.
11. Reset your WordPress site.

Happy fixing!