Gah. That's extremely frustrating. Can I get a Steam version instead somehow? I was really looking forward to it and now I've wasted $40.
You haven't wasted $40 don't worry! The main game works fine right now and the expansion will start to work again soon, we have a test build with a fix in test now, once it passes our checks we'll submit it to Apple.
It's one of the risks of upgrading to a new OS before the first set of OS updates, sometimes new OS's have bugs/issues that need working around.