Typically, this is less a big deal for plugins, in my experience. That being said, you may need to temporarily change the permissions of wp-config.php to be 600 (or more open than that), then enable WP Super Cache, as the plugin will need to modify that file to enable its caching. After the cache is enabled you can set that file back to 400, or leave things be as we have a scheduled job that runs on the server to change wp-config.php files to 400 as a security measure.
Let me know if that helps! If you need us to take a look at a particular WP install, definitely reach out to our support and we can take a look!