Hi @Bill3, This is usually a timing/consent issue: Zoom notes that “If there’s no one in the meeting to approve the app, the RTMS session cannot start”, so if your webhook fires and you call start before the host (or an authorized approver) is actually in the meeting, the request won’t result in meeting.rtms_started.
A practical fix is to delay or retry the PATCH until you see the host join (and treat early joins as “not ready”), using signals like the meeting.participant_jbh_waiting event (“Joined Before Host”) or meeting.participant_joined, and log the PATCH HTTP status/body so you can catch non-2xx responses you might be ignoring.
On the base URL changing it shouldn’t affect the host-first vs participant-first behavior.