Readding audio to a simulation

Hello,

One of our master authors created a simulation with voiceover but later on the sound disappeared from the simulation. She created another file as a test, where the voiceover is added properly.

When I checked the simulation, the sound icon for the simulation slides are missing, however, from 'Audio - Export all Audio Files' I could export the sound files for all the slides.

Is there a simple setting I missed that makes it possible to turn back the sound on for the simulation or do we have to readd all the sound files one by one?

Thank you for your advice in advance.