To enable the Debug menu in Solid Security, you will need to add the code below to your wp-config.php file. You can see how to edit the wp-config.php file in this article.
define( 'ITSEC_DEBUG', true );
Be sure to add the code above the "That's all happy blogging." line.
Then, save the change after adding the line to your wp-config.php file.
Now you will be able to select the Debug menu from your WordPress Admin Bar.