Yes please check using a real device with different media size. Such as if you see the mobile menu by resizing Firefox browser window it's looking opened, and then check it live on your real mobile device.
Another reason if it happens: We gzipped, compressed and cached our code using Joomla Default and JCH optimizer plugin, so Bootstrap media query code will may not work with Firebug or Web developer tools.
Also for a better idea, Please kindly check gantry forum, Gantry complies less code, we should make it enable and off every compressed plugin during development period.
Our demo site is in live and not compatible with any development purpose.