I have been modifying my copy of your theme to work with my client and discovered that on the iphone the menu doesn’t load automatically. Further investigation has led me to try on other small screens with the same issue, if I rotate the screen 90degrees and force CSS to adapt or sometime scroll down and up then the menu will appear. I was easily able to replicate this issue on your very own demo.

Music Booking

Simply load the file with a small browser window, or on a phone and you’ll see that the menu disappears. I was hoping this a simple outdated library but I can’t seem to follow the code enough to find out where it is.

If you could have a look and let me know if there is a temp fix or something to address the issue I’d appreciate it. I assume you’ll need to make the change on your own page and push the fix out to you’re clients.