Enabling Multisite Broke My Database Connection

This is my second multisite installation, yet it didn’t go as easily as the first, even though they’re on the same VPS.

I went through the steps to “Set Up a Network” and upon visiting my site again, it simply says Error establishing database connection.

To be clear, the lines I added to my wp-config.php file are:

define('WP_ALLOW_MULTISITE', true);
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
$base = '/';
define('DOMAIN_CURRENT_SITE', 'www.vpeglobal.com');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

This is my entire .htaccess file:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]

In two locations in the wp_options table the domain is correctly set as https://www.vpeglobal.com and in one location in the wp_site table the domain is correctly set as www.vpeglobal.com.

The database information in wp-config has not changed, and I know that the database is still at localhost with the same credentials.

I’m guessing my mistake is somewhere in the DNS settings, but I’m not sure.