I believe none of the hacks work in the editor, including Bitsy Muse. It is intentional in the sense that the hacks are additions to Bitsy games, not additions to the editor.
To playtest your game with the sound, you'll need to play it in your browser, which you can do! You said you were able to open the html in your browser, so you should be able to play it that way once opened. If you need to make changes due to finding bugs etc in your playtest, then you can go back to the editor, or edit your game file directly if you're comfortable doing so.