wp_enqueue_style in WordPress plugin class not working

IF you want the CSS to be in your plugin’s settings page, you should be using this action: admin_enqueue_scripts, as the action you are currently using is for the front end.

add_action( 'admin_enqueue_scripts', array($this, 'register_plugin_styles' ));

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)