Echo during a Remote LiveShare or Interview session is usually related to the participant and/or the moderator not using headphones with a built-in microphone. Although more rare, echo could also occur even if you are wearing a headset, if the participant and/or the moderator has the volume loud enough for the sound to leak out of the headphones and be picked up by the speakers.
If the above doesn't help, you could also verify that you don't simultaneously have any other platform/functionality active that also uses audio (Zoom, FaceTime, etc)? If so, that could possibly create unexpected outcomes.
You could also check your audio settings, if there's any clarity about whether your audio may be trying to send the audio to both your headset and the speakers, that might cause some issues.
So in short, for best performance and to ensure there is no echo, make sure both the moderator and participant are using headphones WITH a built-in microphone and that the computer is configured to use that headset for both input and output.