Just in case it may help: One possible explanation the game isn't loading is the game is built using Brotli-compression. I believe that doesn't really work with Itch — there may be some server settings missing. Not sure.
Either way, you could try building with Gzip-compression instead, that seems to work. It's Edit › Project Settings › Player › (HTML5 Tab) › Publishing Settings › Compression Format — Then set to "Gzip". [Docs]
Then, hey, that may all be way too much effort : D Cheers!