Many apologies, but it seems that if your main game version was greater than 3.000, it would not install the expansion via our updater. Most people seem to download 3.0 and the expansion at the same time, or get the expansion through services like Steam or Impulse, which is I guess why this never came up until now. I have put out a new beta release,
3.020, which resolves this. If you update to 3.020, then it will let you manually install the expansion or download it automatically, whatever your preference is. Again, my apologies, what a terrible oversight.