Redirect non-members to the Membership Levels page in PMPro if they do not have a membership level.

redirect_non_members_to_levels_page.php

<?php
/**
 * Redirect non-members to the Membership Levels page if they do not have a membership level.
 *
 * 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 redirect_non_members_to_levels_page( $url ) {
	$url = pmpro_url( 'levels' );
	return $url;
}
add_filter( 'pmpro_account_preheader_redirect', 'redirect_non_members_to_levels_page' );