As mentioned here: https://developers.facebook.com/community/threads/423413839738159/

I am setting up a simple app following the Facebook Checkbox implementation guide (https://developers.facebook.com/docs/messenger-platform/discovery/checkbox-plugin/).

However, even though I am logged in with the app admin account, the checkbox plugin fails to render with the following message:

"Your app does not have the permission to message the user. Before approved for pages_messaging permission by App Review, you can only message people who have roles on the app."

The webhooks are setup correctly (tested with the dummy request). The app is added to a page, subscribed to opt-ins and has standard pages_messaging permisions. I'm serving it through a HTTPS site (with ngrok) and have whitelisted in the page settings.

Why isn't this working?