Genesys Cloud webhook for queue SLA breach not firing

Trying to set up a webhook to notify Slack when a queue breaches SLA. Created the webhook via /api/v2/routing/webhooks with event queue.sla.breach. The JSON payload looks correct, but nothing hits the Slack URL. Is there a specific routing configuration needed for this event? The webhook status shows enabled.

{
 "enabled": true,
 "url": "https://hooks.slack.com/services/...",
 "event": "queue.sla.breach"
}