The sound files don't seem to be there. How did you upload them exactly? They need to be included in a zip archive along with the game file (renamed to index.html), paying attention to the relative paths.
Thank you very much! I will try to do this.
I've uploaded the sound files as individual files (.flac and .wav), hidden and not downloadable.
Suspected as much. That wasn't going to work because they end up elsewhere that way.
I've uploaded the game as a zip archive and everything works now! Many thanks!