BCC a copy of recurring payment reminder emails to an additional email address, e.g. admin.

pmpro-send-copy-of-recurring-reminder-to-additional-email.php

<?php
/**
 * Send a copy of an Invoice email i a member has specified and additional invoice email addresses.
 *
 * This recipe require an additional email address to be set in usermeta table.
 *
 * Collecting an additional invoice email address should be achievable with a custom User Field.
 * @link https://www.paidmembershipspro.com/documentation/user-fields/
 *
 * 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_email_headers_bcc_on_recurring_email( $headers, $email ) {
	if ( strpos( $email->template, 'membership_recurring' ) !== false ) {
		//add bcc
		$headers[] = 'Bcc:' . 'otheremail@domain.com'; //change to your email address
	}

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