Hello,
I tried downloading the game after another dev reported the same issue, and my download also "fails"... Or rather, it downloads the first 600mb, then it completes without returning any error.
The other dev tried reuploading the game, but that did not fix the issue. Could be a temporary issue with itch.io, in the meantime you can download the game on Patreon. I'll be putting an external secondary link briefly here on itch.io.
Sorry for the issue!