BCC the admin on Membership Recurring emails.

my_pmpro_bcc_membership_recurring_emails.php

<?php
/**
 * BCC the admin on Recurring Payment Receipt emails.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_bcc_membership_recurring_emails( $headers, $email ) {
	if ( 'invoice' === $email->template ) {
		$headers[] = 'Bcc:' . get_bloginfo( 'admin_email' );
	}

	return $headers;
}
add_filter( 'pmpro_email_headers', 'my_pmpro_bcc_membership_recurring_emails', 10, 2 );