Zoom Recording - phone icon

We record our podcast using Zoom.  For some reason, in a recent recording, when the  guest speaks, only a phone icon shows on the screen, even though for the interview the host could see the guest live on video.  This has never happened. Why is the phone icon showing instead of the guest's face/video? This has never happened.  There was a PR person who called in to listen to the interview but they were on mute.