When creating a Messenger chat bot you must force people to subscribe to your page before they can use it. To do this you need a Secure Callback URL, a standard http:// address won't do, it must be https://
I don't have a Secure Callback URL to my disposal. Can anyone recommend a site/way for me to get one?
You can configure your domain name with cloudflare to use it as a proxy between the user & your webserver.
You can enable their flexible SSL which is free of charge and very easy to configure. You can find more details here and here. I've recently configured my FB Chatbot webhook with cloudflare free SSL and it works pretty well.
