I tried this method and the same error came up. It says "Error 1 Invalid game data."
Viewing post in First alpha build released comments
Another possibility is that the game data and room version are not supported.
Bitsy3D currently only supports Bitsy version 7.10 and room format 1. You may have some luck just manually changing the version of these values in your game data file.
Also, make sure you're using the game data export and not the actual HTML game itself. :)