The reason you cannot update it is that there is not an update to be had yet. Lightroom 3.1 is the current release. I'm not a Mac user. But this "could" be an issue related to your OS. Are you connecting the camera to your computer? Have you tried a card reader? Have you tried using your OS to transfer the images to the hard drive and then import them into Lightroom?
There is Lightroom Classic. It runs under a completely different philosophy. Lightroom Classic utilizes a local catalog, and stores images locally on your hard drive. It has the capability of sharing collections of smart previews with Lightroom for the web.