I'm currently building a chatbot on Facebook messenger and am struggling with implementing the "one time notification" flow.

I can successfully ask the user if they'd like to receive a notification, but I never receive any pingback on my webhook. I made sure my webhook was subscribed to optin events but still nothing. I also made sure my page had access to the One-time notification feature

I've tried checking the permissions all over my facebook account, figuring it must be a facebook-side error for not sending the response to the webhook, but I can not figure it out. I've also tried implementing this from scratch several times to see if I simply missed a step somewhere but no change.