Click the button. Nothing. Here's the two-step diagnosis.
Hey — two things cause this almost every time. Either the MP3 file didn't make it into your deployed output, or the path in your HTML doesn't match where the file actually lives on the server. Both are fast to check.
F12 → Network tab → click your audio button. Watch for the HTTP request. If it says 404 — file not found on the server. Your build script didn't copy the assets/ folder into _site/.
Fix: add assets to your build copy loop and redeploy.
for dir in images css js public assets; do [ -d "$dir" ] && cp -r "$dir" _site/ done
Check what path your HTML uses: src="/assets/audio/pj-main.mp3". Then check where the file actually deployed: ls _site/assets/audio/. One missing folder name in the path = silence, no error.
That's a browser autoplay block. Safari and Chrome require audio to be triggered by a direct user gesture. If your code starts playback on page load or via a timer — it'll be blocked silently. Wire it to an onclick instead.