Sorry, not sure what the problem is here. Perhaps try downloading it from the browser page?
https://adamgryu.itch.io/youre-in-space
I'm not sure why your download manager marks it as forbidden. Are using a special downloader plugin or just the regular browser? Can you download other games from itch.io OK?
I know Windows SmartScreen sometimes marks itch.io games as untrusted since some aren't downloaded very often... could it be that?