My WordPress visual editor disappeared. What should I do?

WordPress detects if the user is on desktop computer or not. If not, then the visual editor will not be rendered out. But the problem is, if you use a proxy or load balancer that strips the user agent, WordPress will assume that you are on a non-desktop device and not render the editor out. To resolve the issue, please open the functions.php file of your current theme and add the following text. 

1. Open /wp-content/themes/ken/functions.php file in the text editor.

2. At the end of the/wp-content/themes/ken/functions.php file, add: 

function user_can_richedit_custom() {
        global $wp_rich_edit;

        if (get_user_option('rich_editing') == 'true' || !is_user_logged_in()) {
                $wp_rich_edit = true;
                return true;
        }

        $wp_rich_edit = false;
        return false;
}

add_filter('user_can_richedit', 'user_can_richedit_custom');