WebSocket `conversation:started` missing in Node SDK subscription

Subscribed to conversation events via the Genesys Cloud Notification API WebSocket using the purecloud-platform-client SDK for Node.js. The connection succeeds, and I get routing:agent:available, but conversation:started never fires. Tried adding the full scope in the auth header and verifying the agent’s status in Architect. Here’s the subscription payload:

{"filters":[{"event":"conversation:started"}]}

What am I missing?