The best way to troubleshoot disappearing icons and buttons is to open the page using a different theme:
- enable allowthemechangeonurl on the theme settings page (admin/settings.php?section=themesettings)
- open the page that is causing trouble adding &theme=clean to the url
If you get the same result, your problem is related to a defective enrolment plugin. If not, your theme is the origin of the problem.