wp_plugin_dir does not work

Hello,

I have installed WP 5.0.3 and checked with PHP 7.3 and 7.2 but I couldn’t make the change in wp-config work for WP_PLUGIN_DIR and WP-PLUGIN_URL It just doesn’t read any plugins in admin panel and doesn’t let me install any either. Please note that I renamed the directory on server to my desired folder name. This is the code I wrote in wp-config

define( ‘WP_SITEURL’, ‘https://’ . $_SERVER[‘SERVER_NAME’] . ‘/test’ );
define( ‘WP_HOME’, ‘https://’ . $_SERVER[‘HTTP_HOST’] . ‘/test’ );

//define( ‘WP_PLUGIN_DIR’, dirname(__FILE__) . ‘/test/wp-content/newplugins’ );
//define( ‘WP_PLUGIN_URL’, ‘https://’ . $_SERVER[‘HTTP_HOST’] . ‘/test/wp-content/newplugins’ );

I have spent hours but couldn’t find a fix even online. Is this caused by new WP version or what? I checked with WP 4.9.9 but same result. Is this PHP 7.x then? Because I have my other websites perfectly working using PHP 5.6 and older versions of WP. I need this done to ensure security so please advise.

Thank you.
Tab