Error establishing a database connection

Recently tried deleting my network per the info layed out at https://www.dummies.com/how-to/content/how-to-disable-a-wordpress-network.html I deleted pp_blogs, pp_blog_versions, pp_registration_log, pp_signups, wp_site, wp_sitemeta and also removed the
define(‘WP_ALLOW_MULTISITE’, true); in my wp-config.php file

After doing the the site divesummit.com went down with the error “Error establishing a database connection”

Luckily I backed up the entire database before I made these changes so I went ahead and imported the database back and re added the define(‘WP_ALLOW_MULTISITE’, true);
Still I am getting the “Error establishing a database connection”

Please advise

Thanks!