What to do, if a Live Photo is Silenced in Photos for Mac
When you notice, that a Live Photo is no longer playing any sound, you may want to check, if you have added any Live effect. Adding the Live effects Loop" or "Bounce"will shorten the video clip and trim it to the the most stable section, and then the Live Photo will be silenced.
To bring the sound back revert the Live Photo to the original:
See: Edit photos and videos on iPhone - Apple Support.
To revert to the original image:
- Open the edited image.
- Tap Edit, then tap Revert.
- Tap Revert to Original.