Can you elaborate? What happens when you try to download it? And are you download via the browser or the app?
Very strange, I'm not sure what's happening since it seems to be working fine for me. You can try downloading and installing manually without using the itch app from https://cosmoteer.net/. If that works for you, then that would indicate it's specifically a problem with the itch app that I can't do anything about, and Itch support might be able to help.