Thank you all for your patience and understanding. We have found the reasons of this issue and are still working on it. ios 16 recently changed the video format they supported leading to not able to play sound in the video. The sound is recorded no problem and you should have no problem hearing sound from any non-ios 16 devices. If you do have similar issues on any non-ios16 devices, please kindly let me know since it might be different issues.
Thank you again for your support!