Webhooks for presence channels are specifically delayed in order to debounce temporary disconnections and member removals. If a user disconnects and then reconnects within 3 seconds, neither event will be delivered via webhook.
Another scenario is when there are multiple connections with the same user_id, they are treated as the same user; webhooks won't be triggered for all events on all sockets.
There is another scenario where your server which receives webhooks is down. Your server should respond to the POST request with a 2XX status code to indicate that the webhook has been successfully received. If a non 2XX status code is returned or the endpoint can’t be reached, Channels will retry sending the webhook, with exponential backoff, for 5 minutes.
If you are experiencing a problem with webhooks not being sent in any other scenario, please provide screenshots or logs (it would be useful to know specific times that you are aware the problem is occurring) with details before contacting us at firstname.lastname@example.org.