Hi @amalwa
Thanks for reaching out to the Zoom Developer Forum and welcome to our community!
Could you please point me toward the documentation that you are using here so I can take a closer look into this?
Essentially what the documentation says is that the event will contain a single ParticipantPropertiesPayload, however, its an Array of ParticipantPropertiesPayload.
If you go into the documentation and navigate to on function, you will see that there is a event that customers can subscribe called - "user-added" which returns information about the user added to the meeting. The response payload is supposed to be an object but its actually an Array.