Webhook not working

We have created a custom app for my client and somehow we have our server down for couple of days few months ago.
After that our webhook stopped working.
Shopify support says its not an issue on their end, but we are not getting request anymore on the server from Shopify. If we try to hit the URL using Postman then it works fine.

I think Shopify has blocked the IP or domain, if we subscribe a new domain then it works fine.

Deleting and creation of webhook by API and Settings is already done multiple time.

Can anyone help me on that?

Webhooks are removed by Shopify if they are unable to be delivered after a specific period. Given the amount of downtime you had, I suspect this is what has happened.
You’ll therefore need to re-add any webhooks that have been deleted.

Webhooks are retries up to 8 times, after multiple failures in a 24 hour period the webhook subscription will be removed.

I have already mentioned, I have deleted & re-added more than 10+ times, even with API’s & from settings as well.

There might be a silent outbound “firewall” by Shopify if other domains are working at receiving the webhooks.

Or alternatively, maybe your own infra is accidentally blocking these requests. I would double check your Cloudflare or WAF settings to make sure DDoS protection isn’t accidentally blocking Shopify webhook requests.

If you have a smart WAF, it’s possible it linked the downtime on your server to the Shopify webhooks, and you’ll need to disable the rule.

Otherwise, if you really believe it’s something on Shopify’s end, then opening up a partner ticket is the best way to go.