This plugin forces the billing address to always be collected at checkout
<?php
/*
 * Plugin Name: Easy Digital Downloads - Force Billing Address
 * Description: This plugin forces the billing address to always be collected at checkout
 * Author: Easy Digital Downloads
 * Author URI: https://easydigitaldownloads.com/
 * Version: 1.0
 */

function pw_edd_force_billing_address() {
	if( ! did_action( 'edd_after_cc_fields', 'edd_default_cc_address_fields' ) ) {
		edd_default_cc_address_fields();
	}
}
add_action( 'edd_purchase_form_after_cc_form', 'pw_edd_force_billing_address' );
To implement this snippet on your site, create a brand new, empty WordPress plugin and paste the above code inside.