It might be, especially if they’re ‘old’, and purchased through iTunes, encoded with DRM, which Sonos can’t ‘read’. If they were originally purchased through iTunes (now called Apple Music), I’d copy them to another directory (temporarily, so in case it doesn’t work, you haven’t lost them), and try downloading a ‘fresh’ copy from Apple. Many years ago, Apple abandoned DRM, and removed it from their downloads, but if you’d previously downloaded a copy, they didn’t automatically update it. I remember days of updating my stuff.
Anyway, try downloading a ‘new’ copy, and see if that works.
