Thank you so much! I will get that fixed asap. I don't understand how the links that were officially shortened for App Store can stop working, but somehow they did. It's unfortunate that this could've been broken for a very long time now, it's just not something I would think of periodically verifying that it's still working.
One idea for catching this sort of break in the future is monitoring the source people use to acquire your app. It looks like the App Store might support tracking which website referred people to download your app: