https://api.acoustid.org first shows a cert for www.acoustid.org, and then it redirects to acoustid.org. No API results at any point. http://api.acoustid.org (which is what's currently in the scripts) gets rejected as loading insecure content via XHR, at least by my browser.
So, two things need to happen:
a.) acoustid API needs to be accessible over https with a valid certificate
b.) MBS needs to use scheme-relative links for loading acoustid API data in root/recording/fingerprints.tt