WordPress: Why isn’t my stylesheet being enqueued?

I’m modifying an existing WP plugin by making a separate plugin that will extend it. I’d like to write CSS that will override the plugin. However, when I try to enqueue the stylesheet it doesn’t work. I know it doesn’t work because I added a simple form in the includes() and tried to style the words red in order to see a change. Why isn’t this working??

Note – I’m using the action hook plugins_loaded, which I read in the codex happens before wp_enqueue_script. So I don’t suspect that my enqueueing is missing the timing, but I’m new to WP dev so correct me if I’m wrong.

Update – Please see my updated CSS code below. The #id selector wasn’t coloring the text red by itself, but when I added the p (paragraph selector) it worked. Neither selector worked by itself, it only worked when I added both. Why is this?

find-do-for-anspress.php

if (! defined('WPINC')) {
    die;
}

Class Find_Do_For_Anspress {

    /**
     * Class instance
     * @var object
     * @since 1.0
     */
    private static $instance;

    /**
     * Get active object instance
     *
     * @since 1.0
     *
     * @access public
     * @static
     * @return object
     */
    public static function get_instance() {

        if ( ! self::$instance ) {
            self::$instance = new Find_Do_For_Anspress(); }

        return self::$instance;
    }
    /**
     * Initialize the class
     * @since 2.0
     */
    public function __construct() {

        if ( ! class_exists( 'AnsPress' ) ) {
            return; // AnsPress not installed.
        }
        if ( ! defined( 'FIND_DO_FOR_ANSPRESS_DIR' ) ) {
            define( 'FIND_DO_FOR_ANSPRESS_DIR', plugin_dir_path( __FILE__ ) ); 
        }

        if ( ! defined( 'FIND_DO_FOR_ANSPRESS_URL' ) ) {
            define( 'FIND_DO_FOR_ANSPRESS_URL', plugin_dir_path( __FILE__ ) );
        }

        $this->includes();

        add_action( 'wp_enqueue_scripts', array($this, 'fd_enqueue'));


}

    private function includes() {

        require_once (FIND_DO_FOR_ANSPRESS_DIR.'braintree/lib/braintree.php');
        require_once (FIND_DO_FOR_ANSPRESS_DIR.'fd-braintree/fd-bt-keys.php');
        require_once (FIND_DO_FOR_ANSPRESS_DIR.'fd-braintree/fd-process-trans.php');
        require_once (FIND_DO_FOR_ANSPRESS_DIR.'fd-braintree/fd-bt-functions.php');
        require_once (FIND_DO_FOR_ANSPRESS_DIR.'fd-braintree/fd-bt-form.php');
        require_once (FIND_DO_FOR_ANSPRESS_DIR.'includes/fd-ask-form.php');



    }

    public function fd_enqueue() {
        wp_enqueue_style( 'fd_for_anspress_css', FIND_DO_FOR_ANSPRESS_DIR.'css/fd-css.css', array(jquery), null); //handle, source, dependencies, version, media (the type of media for which the stylesheet is designed, e.g. mobile, web, print...)
        //wp_enqueue_script( 'fd_for_anspress_js', FIND_DO_FOR_ANSPRESS_DIR.'fd-braintree/js/fd-braintree-js.js', array(), null);  used require_once to directly add it to fd-bt-form.php
    } 

} //End class

function find_do_for_anspress() {
    $FDClassStart = new Find_Do_For_AnsPress();
}
add_action( 'plugins_loaded', 'find_do_for_anspress' );

        //HTML "testing" block
        echo '<p id="checkout">Testing the enqueued CSS</p>';

fd-css.css attempt 1

<style>
#checkout {
    color: red;
}
</style>

fd-css.css attempt 2

<style>
#checkout {

    color: red;
}

p {
    color: red;
}
</style>