I ran into a no sound issue when importing a Construct 2 project and exporting with advanced minify setting.
Same project exported with simple minify setting works fine.
Previews worked fine, only after uploading to a site discovered that there was no sound.
This seems to be a bug. Possible workaround, re-import sounds and let Construct 3 convert ( did not try it ).
Your case may be different, but try minify/simple setting