Cobrowse session initiation failing with 400 via Conversations API

I’ve been trying to kick off a cobrowse session programmatically using the Genesys Cloud Conversations API, but I’m hitting a wall with a 400 Bad Request. The goal is to trigger this from an external service rather than through the UI, so I’m using the POST /api/v2/conversations/{conversationId}/cobrowse endpoint. I’ve got a valid OAuth token with the cobrowse:control scope, and the conversation ID is definitely active and of type webchat.

Here’s the payload I’m sending:

{
 "type": "cobrowse",
 "settings": {
 "isInteractive": true,
 "isFullPage": false
 }
}

The response comes back with:

{
 "errors": [
 {
 "code": "invalid_request",
 "message": "Cobrowse session cannot be initiated for this conversation type or state."
 }
 ]
}

I’ve checked the documentation, and it seems like this should work for webchat. I’ve also verified that the participant on the other end has the cobrowse capability enabled in their profile. I’m wondering if there’s a specific state the conversation needs to be in, or if I’m missing a required field in the request body. I’ve tried adding the sessionId in the payload, but that just throws a different error about the session not existing. I’m using the Python SDK to make the request, but I’ve also tried hitting the endpoint directly with Postman to rule out SDK issues. Same result either way. I’m not sure what I’m missing here.