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).
Oh man I've been struggling with event spawners and Qmovement compatibility for quite a while- went as far as to use a tool just to pick crops but Ritter got their spawner to work with Qmove and I'm screeing! It's still in testing period but just- the feeling of getting over a large gameplay hurdle is a HUGE relief, I'm so thankful to Ritter! It's a cheap paid plugin but totally worth it!