Unfortunately, that sounds like something we can't fix on our end. I just tested downloading the windows version of the game and it worked alright, so the file is definitely there and itch.io should still be working just fine.
A download failing to finish could mean an overzealous antivirus, or problems with the browser you're using. Here's a slightly old guide from Itch.io that might be able to help, but unfortunately it sounds like whatever problem you've got is something that can't be fixed on our end.