Question: Why don't I hear the other party in my MacOS video call recording?
Answer: If you don't here the other party in your MacOS video call recording, it's likely you were making a Full Screen recording rather than a Browser Tab recording.
NOTE
If a recording does not have the desired audio, the audio cannot be recovered.
Due to system limitations imposed by Apple, it's impossible to record system audio on Macs (the sound coming from your computer during a full screen recording).
To record the sound coming from your computer on a Mac you will need to make a "Browser Tab" recording.