Call queue webhooks not being sent

We've subscribed to voicemail webhooks for the call queue's extension, but are not receiving any notifications via webhooks when a call comes into the call queue and goes to voicemail.

If I call the company line and enter an extension and it goes to voicemail, I get the webhook.

Are webhooks not working for call queue extensions?

Here is the subscription:

{
  "uri": "https://platform.devtest.ringcentral.com/restapi/v1.0/subscription/40cc2bc7-9ea6-49aa-8dc0-6960545b8455",
  "id": "40cc2bc7-9ea6-49aa-8dc0-6960545b8455",
  "creationTime": "2019-07-12T22:14:40.810Z",
  "status": "Active",
  "eventFilters": [
    "/restapi/v1.0/account/261039004/extension/262983004/voicemail"
  ],
  "expirationTime": "2019-07-19T22:14:40.810Z",
  "expiresIn": 604243,
  "deliveryMode": {
    "transportType": "WebHook",
    "encryption": false,
    "address": "https://www.gaugely.com/incoming/ringcentral"
  }
}