shfx,
I think checking for updates (via the menu, I think the Help menu) was a fairly recently added feature. You'll probably need to just go to
http://www.simplify3d.com/downloads directly, enter your software key, pick your OS, and click Download to receive the latest. Uninstall the one you have (don't worry, you don't need to remove your activation first), then install the new one.
Dale