Installing Multi Site in sub domain – Database Issue

I have my main site as a single WP installation
URL : https://www.loofynhyper.com

I tired to install WordPress Multi site in the sub domain https://demo.loofynhyper.com/
and planning to have the sub-sites in the following URLS
https://demo.loofynhyper.com/site1
https://demo.loofynhyper.com/site2
…

But went i change the WPconfig file with the following code i’m getting database error (Error establishing a database connection)

define( ‘WP_ALLOW_MULTISITE’, true );
define( ‘SUBDOMAIN_INSTALL’, true ); // If i change this to “false”, website is loading but as a single wp installation, not as multisite.
define( ‘DOMAIN_CURRENT_SITE’, ‘demo.loofynhyper.com’ );
define( ‘PATH_CURRENT_SITE’, ‘/’ );
define( ‘SITE_ID_CURRENT_SITE’, 1 );
define( ‘BLOG_ID_CURRENT_SITE’, 1 );

Not sure how to resolve the issue, please help me out if you cloud understand the issue. Thanks.

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