This is weird this error happen only if you don't enter the local server created by the Helper exe (http://localhost:8000/)
I wanted to make it html because it's easier for people to play it but got an issue (different than the size one) that was blocking the upload on any website, so I uploaded (by luck after few hours of the 1st deadline because it was also blocking its upload xD) the zip before going to sleep.
If I knew I'd have this issue at the beginning I would have gone for a standalone in the late version of the engine 😅