With your theme installed, I have come to write a new post, and when I click the shortcode generator icon, I recieve an error.
You don’t have permission to access /wp-content/themes/HighendWP/includes/tinymce/hbthemes-shortcodes-iframe.php on this server.
Version of WordPress : 4.9.5
Version of HighEnd : 188.8.131.52
I have logged into the backend, and if you review the screenshot it shows the permissions that are currently setup on that folder.
I look forward to hearing from you soon