If your app isn’t listed in Auto-start apps and meeting.rtms_started never fires, RTMS likely isn’t enabled for your account/app yet. Zoom’s published onboarding flow is to submit the 30-day free trial form, then the Developer Advocacy/Sales team enables RTMS on your account.
Once RTMS is enabled, the dropdown should only show RTMS-enabled apps, and you can select it under Auto-start apps that access shared real-time meeting content (with “Share realtime meeting content with apps” enabled).
Also webhook delivery depends on RTMS actually starting in the meeting: make sure you’re subscribed to meeting.rtms_started / meeting.rtms_stopped and that your endpoint passes Zoom’s webhook configuration and validation requirements.
If it helps, we’ve supported thousands of Zoom implementations at Recall.ai (an official Zoom RTMS partner) and can help you with your RTMS integration/setup once someone on the Zoom team confirms RTMS is enabled on your account.