checkbox function not working for dropdown menu

I have created a dropdown menu that shows when a checkbox is clicked.

It works perfectly outside of wordpress see JS Fiddle - http://jsfiddle.net/s7w2ueah/

however when I add it into my WP theme ( running blankslate ) the checkbox function does not work ( I assume it is the checkbox function) - I have run it on a number of different themes to no avail which makes me think that this is a problem on all wordpress themes.

I have an example of it here on an existing website running wordpress twenty fourteen.

How can I make the menu drop down ?

Cheers