Demo Site Errors

I expect you are aware, but if not I’m reporting it since this looks like a well regarded plugin, having the demo site throw error is a turn off…. See below:
https://demos.paymentplugins.com/wc-stripe/product/pullover/

Warning: mysqli_real_connect(): (HY000/2002): Connection refused in /var/www/demos.paymentplugins.com/wc-stripe/wp-includes/wp-db.php on line 1753

Connection refusedError establishing a database connection

This either means that the username and password information in your wp-config.php file is incorrect or we cant contact the database server at localhost. This could mean your hosts database server is down.

The page I need help with: [log in to see the link]