you forgot to enable the http support on the page, the zip on it's own does nothing. You have to check the box on the zip that it works in the browser.
Viewing post in Coloroid jam comments
Unfortunately, I didn't forget, instead it seems like something is broken with Itch.io's loader, making the HTML5 upload not function. :( I'm fairly certain it's not my actual zip, because I can download and extract it locally, and it works fine in-browser. I've reached out to itch.io support regarding it, but haven't heard back, and I also can't upload a new version during the jam. Ah well.