I've moved this thread to RPG Maker MZ. Please be sure to post your threads in the correct forum next time. Thank you.
The engine doesn't support MP3 by default. It does support ogg. Try adding the SE to your project's folder manually and see if you can read it in the engine. Also don't forget that the filename and file path must follow HTML5 rules (no spaces for instance).
Thanks for your review.
I was checking the trailer for details and as the woman shut the door at the exact moment the song I was hearing said "you slim the door" and I couldn't resist to add it there. And I used this idea one more time on another scene.