The mobile menu works fine on my Reddle test site so I'd first recommend reinstalling a fresh copy of the theme.
Just a heads-up that if you edited any of the theme files directly, please be careful to make a backup of your files first, as all your changes will be overwritten.
I'd suggest moving your tweaks into a child theme so your tweaks won't be overwritten every time you update the theme. Here are some guides in case you haven't made one before:
http://codex.wordpress.org/Child_Themes
https://www.smashingmagazine.com/2016/01/create-customize-wordpress-child-theme/
http://vimeo.com/39023468
If reinstalling a fresh copy of your theme doesn't fix the issue, you could try temporarily deactivating all your plugins. Does the problem persist? If the problem is gone, reactivate your plugins one-by-one, look at the site in between each reactivation, to find the conflict.