POST /api/v2/conversations/calls 403 Forbidden when initiating outbound call via Terraform

NICE CXone API & Integrations
1

We are trying to initiate an outbound call on behalf of an agent using the Genesys Cloud Conversations API. The endpoint is POST /api/v2/conversations/calls. We have the necessary OAuth scopes, but the response is a 403 Forbidden error. The request payload looks like this:

{
 "from": { "phoneNumber": "+1234567890" },
 "to": [{ "phoneNumber": "+0987654321" }],
 "wrapUpCode": "completed"
}

The agent is logged in and has the correct permissions. Has anyone encountered this issue before? What could be causing the 403 error?