We're not sure what's causing the issue.
We've already checked the zip archive for any errors in the upload folder on itch, and it seems to be in good shape.
Interestingly, we also couldn't download the entire 10 GB through the website, so we suggest trying to download it via the itch.io launcher instead.
We did re-upload the build, but itch didn't register any changes in the file, indicating that the original file was uploaded to itch without any problems.