Sound on Device

Have you searched the Docs and Knowledge base?
Principle Version: 5.8
macOS Version: 10.14.5
Sketch Version: N/A
Description of what you need help with:
I have created a principle walk through that includes animations with sound. The animations with sound are MP4s. When I play the animation with sound on the principle ‘show preview,’ I can see the animation and hear the sound. When i use the prototype on the iPhone x the animation shows great but i am unable to hear any sound. (yes, i checked the volume)

Steps to reproduce the behavior:

  1. build prototype with animation and sound
  2. put build device
  3. use prototype on iPhone X

Screenshots/Sketch File/Principle file: (if applicable)