Hey,  It's sad it doesn't display install instruction on submission page but it's on the main page of the project.

In the zip archive you have a  .exe named  "HTML5LaunchHelper.exe", you launch it it will start a local server.
In your browser you enter the link      http://localhost:8000/    and it will open the access of the project folder and from this you click on the index.html  to launch the game. 

Its a shame too because it looks cool - perhaps try and just use a packaged format next time? Im not sure what benefits HTML5 offers over a standalone.exe when you arent talking about multiplayer. 

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   😅

Hello, thank you and yes older version can package to allow us making webgames and probably 4.27 but you have to go manually from their github.

(I used UE 4.23 for that one)