When a webhook request returns a status code other than 200/201 that request is considered to have failed. The webhook will retry the request 9 times, after which it will be marked as permanently failed. Each retry is multiplied by 30 seconds, eg the first retry will be 30 seconds after the first request, the second retry after 1,5 minutes, and so on.
When a single webhook has 10 permanently failed requests within 5 minutes, the webhook will be deactivated.