Spotify ok but no sound from NAS mount

Couldn’t find any similar problem, so here it is:

  • Volumio 1.55 works fine with Spotify on my Pi+hifiberry DAC
  • I can mount a NAS volume from a local network drive, no fancy option; library successfully updates with all the tracks from that volume
  • No sound output when playing any of those NAS volume mp3 files. Playback says music is indeed streaming, but no sound.

Weird, IMHO. Any hint ?