Another twentytwelve menu button issue with iphone

In my twentytwelve site, http://sfwomenartists.org/wp/, the menu button that shows up on my iphone 6 and on my old Android Galaxy3 – will not ‘depress’ and does not produce a menu. However, on the sub-site, http://events.sfwomenartists.org with a separate WP installation, also twentytwelve, it works perfectly fine. I can’t see anything different that I’ve done. In fact I copied all the theme files over from the sub-site to the ‘mother’ site when I upgraded the latter from twentyeleven.

Can anyone help me troubleshoot this issue? sfwomenartists.org is a hybrid site so the issue only shows up on the News and Members Area pages plus several others not in the main nav menu. The static page menus just reduce in the phones and work OK.

Thanks for any help.