Announcements (MP3) not working

Hi

Trying to get a doorbell sound to play as announcement on my Sonos players. Just trying one player for now. File shows up fine and log makes it look as if it’s doing the right things - figures out length of the mp3, sets volume, plays etc. But I don’t hear anything. I just get seven seconds of silence. Any clues?

What does your announcement screen look like:
Click for large view - Uploaded with Skitch

Pretty much the same although instead of using Amazon/Polly I have tried with an MP3 file. I've also tried using the Apple voice. Again, all looks fine in the log but no sound. Have also tried with different Sonos players around the house, but nothing.