Chromebook is a variation of the Linux operating system.
Among Us only supports Windows, so I don't really understand how your Son was able to play the Game without using Tools like WINE or Proton.
I suggest to look at this tutorial: https://beebom.com/install-play-among-us-on-chromebook/
A lot of different ways of playing the game on a chromebook are described here. Maybe one of them works for you?