Are you pressing the "Run game" button? Which browser and OS are you in?
This is what it says when I launch the game. I now have both files downloaded.
Unable to parse Build/Build.framework.js.br! This can happen if build compression was enabled but web server hosting the content was misconfigured to not serve the file with HTTP Response Header "Content-Encoding: br" present. Check browser Console and Devtools Network tab to debug