Ok, it is not the theme (tested it fresh).
(Asking : you DO see the layout and its areas in screen???)
So you do NOT see the 'dropdown box'?
If this is the case some things are not loaded or not called.
Best to use the recently new add ons for Chrome (https://chrome.google.com/webstore/detail/e107-dev/ikpmmbnjfndjmpmehlgeeinfkiaafdkf) or the one for Firefox..(https://addons.mozilla.org/en-US/firefox/addon/e107-dev/) and activate it on site (best logged in) it will try to help you finding this cause.
You can run checks and plugin scan etc under admin/tools/ see left column.