Dropdown menu won't expand – spacious theme

I am using the spacious theme. I have used this theme for several sites and am only experiencing this problem on http://www.jcslittlebigband.com/wp_admin

The hamburger menu will not expand on a small screen/mobile device. I have copied menu code from other sites where it is working and inserted it into the site but it has not fixed the problem. I have searched the forums and nothing I have tried has fixed it.

I really need this working as quickly as possible.

Thanks in advance.