If the shortcode “D” button is not coming at your editor, there may be two settings issue.
1. JS folder permission issue at your server.
Go to your root directory> Prestashop, then find “JS” folder set full open permission for that folder.
2. “tinymce.inc.js” file manual replacement issue.
Inside of your modules>smartshortcode>js>lib location, there is a file named “tinymce.inc.js” .
Copy that “tinymce.inc.js” file and replace that inside of your root>prestashop>js folder.
Your issue should be solved then.Before checking, make sure all of your prestashop cache,module cache and server cache are cleared properly.