itch.io

Hi! I think I might be able to help a little bit (though I think you'd need to contact the jam organisers to have any chance of fixing the game over on itch - hopefully the gd.games version is enough to count for the jam).

Based on the huge number of files you have available for download here, I think I see what's gone wrong. To get an HTML5 build to work, you need to combine all the files that GDevelop produces into a single zip file. Basically, use the option to produce a web game and there should be an option to "view files in folder" (or something very similar). You'll need to select all of those (Ctrl+A will typically do the job), then right-click one of them. There should be an option for something like "Compress" (or possibly "Send to..." which should give you one option called "compressed zipped folder). All in all, it seems as though you have all the files you'd need for this to work as a web game, they're just not arranged in a way that itch can deal with.

In case it helps, this video shows roughly what you should be looking for, though it skips over it very quickly at about 2:35: