MadHat mobile menu shows black bar with grey “Navigation” button, not menu items

Hi Everyone – linking 5 images in a Google Drive folder, in hopes someone can help tell me why my MadHat theme menu looks the way it does on my iPhone, when it displays fine on the other two devices:

https://drive.google.com/open?id=0BywI7wa0XG99M05iOGRVdWJXZHc

Any help is greatly appreciated. I’m using:

Macbook Pro
iPadAir 1
iPhone 6