Information
Participants who belong to your account can see that a guest (someone who does not belong to your account) is participating in the meeting/webinar. The Participants list indicates which attendees are guests. The guests themselves do not see that they are listed as guests.
Rationale:
Solution
Go into the Zoom Admin Dashboard on the zoom website. Account Management -> Account Settings -> Meeting -> In Meeting (Advanced) -> Identify guest participants in the meeting/webinar, and ensure it is enabled.