Primary menu doesn't show on iPhone

Hi, thanks for a great theme! I just noticed that my site is misbehaving on the iPhone, whereas I'm sure it worked at one point. The primary menu looks fine in Safari on the Mac even when I shrink it down to the smallest width (540px). Google Chrome lets me shrink it even skinnier, all good. It also looks great on iPad. But that primary menu never shows on iPhone for some reason. http://aliciabessette.com I tried disabling the WP Menu Cart plugin but it made no difference. I'm not using the JetPack mobile module. Any ideas? Thanks!