The loop option should be there. You can edit your song and go to the master tab and select that audio file. Then click on Inspector and go to Media in the inspector and set the looping there.
But, if the audio is added as a foreground element, the looping feature should be there in the live window when you're live to it like this
Is there any way to add music to a song that loops.
We have a welcome slide and a short piece of audio added to the master slide. I can see play and pause controls but not loop.