We have made plugin that requires webhooks and we noticed that some shops that has our plugin installed does not send webhooks back to us. Upon investigation we found that there are no registered webhooks for those shops.
When we register webhook through API we get good response. For example:
Hello, it looks like many of the webhooks from your shop were retried 19 times and deleted, If there are 19 consecutive failures, then the webhook subscription is automatically deleted. This is likely why you are unable to see them. This could be an issue with the destination you're sending webhooks to, for example it could be down and not responding. For more information on this have a look at the "Responding to a webhook" section at this link: https://shopify.dev/tutorials/manage-webhooks