Corrected plugin.php from https://wordpress.org/support/topic/error-messages-on-new-site-after-changing-slugs/

plugin.php

<?php
/**
 * Main Plugin File
 *
 * @package genesis-portfolio-pro
 */

/**
 * Plugin Name: Genesis Portfolio Pro Custom Slugs
 * Plugin URI: https://wordpress.org/plugins/genesis-portfolio-pro/ modified
 * Description: Adds default portfolio to any Genesis HTML5 theme. Alters Genesis Portfolio slugs.
 * Version: 1.2.3
 * Text Domain: genesis-portfolio-pro-custom
 * Requires at least: 4.4
 * Requires PHP: 5.6
 * Domain Path: /languages
 */

namespace GPPCS;

require_once plugin_dir_path(__FILE__) . 'genesis-portfolio-pro.php';

add_filter('register_taxonomy_args', 'GPPCS\portfolio_type_args', 10, 2);
/**
 * Change Genesis Portfolio Type arguments.
 *
 * @param array $args Taxonomy arguments.
 * @param string $taxonomy Current taxonomy.
 * @return array New taxonomy arguments.
 */
function portfolio_type_args( $args, $taxonomy ) {
	if ( 'portfolio-type' === $taxonomy ) {
		$args['rewrite']['slug'] = 'meeting-type';
		$args['labels']['name'] = _x('Meeting Types', 'taxonomy general name', 'genesis-portfolio-pro');
		$args['labels']['singular_name'] = _x('Meeting Type', 'taxonomy singular name', 'genesis-portfolio-pro');
		$args['labels']['search_items'] = __('Search Meeting Types', 'genesis-portfolio-pro');
		$args['labels']['popular_items'] = __('Popular Meeting Types', 'genesis-portfolio-pro');
		$args['labels']['all_items'] = __('All Types', 'genesis-portfolio-pro');
		$args['labels']['edit_item'] = __('Edit Meeting Types', 'genesis-portfolio-pro');
		$args['labels']['update_item'] = __('Update Meeting Types', 'genesis-portfolio-pro');
		$args['labels']['add_new_item'] = __('Add New Meeting Types', 'genesis-portfolio-pro');
		$args['labels']['new_item_name'] = __('New Meeting Type Name', 'genesis-portfolio-pro');
		$args['labels']['separate_items_with_commas'] = __('Separate Meeting Types with commas', 'genesis-portfolio-pro');
		$args['labels']['add_or_remove_items'] = __('Add or remove Meeting Types', 'genesis-portfolio-pro');
		$args['labels']['choose_from_most_used'] = __('Choose from the most used Meeting Types', 'genesis-portfolio-pro');
		$args['labels']['not_found'] = __('No Meeting Types found.', 'genesis-portfolio-pro');
		$args['labels']['menu_name'] = __('Meeting Types', 'taxonomy menu name', 'genesis-portfolio-pro');
	}

	return $args;
}

add_filter('register_post_type_args', 'GPPCS\portfolio_args', 10, 2);
/**
 * Change Genesis Portfolio arguments.
 *
 * @param array $args Post type arguments.
 * @param string $post_type Current post type.
 * @return array Filtered post type arguments.
 */
function portfolio_args( $args, $post_type ) {
	if ( 'portfolio' === $post_type ) {
		$args['rewrite']['slug'] = 'meeting';
		$args['labels']['name'] = _x('Meetings', 'post type general name', 'genesis-portfolio-pro');
		$args['labels']['singular_name'] = _x('Meeting', 'post type singular name', 'genesis-portfolio-pro');
		$args['labels']['menu_name'] = _x('Meetings', 'admin menu', 'genesis-portfolio-pro');
		$args['labels']['name_admin_bar'] = _x('Meeting', 'add new on admin bar', 'genesis-portfolio-pro');
		$args['labels']['add_new'] = _x('Add New', 'Meeting', 'genesis-portfolio-pro');
		$args['labels']['add_new_item'] = __('Add New Meeting', 'genesis-portfolio-pro');
		$args['labels']['new_item'] = __('New Meeting', 'genesis-portfolio-pro');
		$args['labels']['edit_item'] = __('Edit Meeting', 'genesis-portfolio-pro');
		$args['labels']['view_item'] = __('View Meeting', 'genesis-portfolio-pro');
		$args['labels']['all_items'] = __('All Meetings', 'genesis-portfolio-pro');
		$args['labels']['search_items'] = __('Search Meetings', 'genesis-portfolio-pro');
		$args['labels']['parent_item_colon'] = __('Parent Meetings', 'genesis-portfolio-pro');
		$args['labels']['not_found'] = __('No Meetings found.', 'genesis-portfolio-pro');
		$args['labels']['not_found_in_trash'] = __('No Meetings found in Trash.', 'genesis-portfolio-pro');
	}

	return $args;
}