Hello,
there was a bug (or missing feature) some time ago which prevented Chromium playing MP3s at least in NW.JS exports of Construct3 projects..
See here:
github.com/Scirra/Construct-3-bugs/issues/1343
It's a while back, but I still seem to be unable to get my MP3s working in NW.JS exports (Win64 to be more precise).. is this the intended behaviour? I don't have an example project at hand (yet), but it's pretty straightforward.. MP3 are played when starting the project within the editor, but not after export.. doesn't matter if zipped, assets packed or whatever.
Release r108.2 beta