I was just checking this. As far as I know, if a game isn't tagged correctly, downloading it through the app can cause that error. But mine is tagged, so I'm not sure why the issue is happening. If it isn't a bug with the itch.io app, I honestly don't know what else could be.
I'm glad you could download it on the website, though! Hope you enjoy it, and thanks for the support! ❤️