Presence webhook does not work on production

I have created an application on sandbox with Subscription and Read Presence permissions. Created a subscription to listen for inbound calls and send a webhook request to our server. All worked fine in sandbox (i.e called the sandbox number and received the payload as expected). I have graduated the app to production and registered the same webhook, but it doesn't work. I am not getting any hits to the registered endpoint, even though calls are constantly being made to the company