Facebook Messenger webhook setup, but not triggered

I have recently worked with the new chat bot API and there's a lot that can go wrong. So, here are some Ideas.

• Make sure you've verified your webhook under the product settings tab.
• subscribe your app to the page using your page access token. It returns {"success" : "true"} if everything goes right.

Important

• Make sure the Facebook user from which you're sending the message is listed as the Admin or Developer or Tester in your app roles (https://developers.facebook.com/apps/YOUR_APP_ID/roles/). Messages from other users won't work unless your app is approved and publicly released.

• Have you received any call back from the facebook api ? or is it just the messages? Take a look at the logs of your web server and check if you're getting any hits on the webhook. Also check the error logs.

• Try hitting your webhook manually and see if it responds. You can use curl to generate a manual request. This is what the request from Facebook looks like:

Command:

curl -i -X POST -H 'Content-Type: application/json' -d '{"object":"page","entry":[{"id":43674671559,"time":1460620433256,"messaging":[{"sender":{"id":123456789},"recipient":{"id":987654321},"timestamp":1460620433123,"message":{"mid":"mid.1460620432888:f8e3412003d2d1cd93","seq":12604,"text":"Testing Chat Bot .."}}]}]}' https://www.YOUR_WEBHOOK_URL_HERE

So my issue was I was calling GET when trying to subscribe instead of POST

https://graph.facebook.com/v2.6/:pageid/subscribed_apps?access_token=:token

GET will return the current subscriptions (empty {[]}), POST returns {"success" : "true"}

Some other gotchas I hit were,

• the examples use https://graph.facebook.com/v2.6/me/.. but I seemed to need to use, https://graph.facebook.com/v2.6/:pageid
• the access token is the messenger access token, not your API access token
• if your webhook throws a error, Facebook will stop sending you messages for a while

One thing I'm still puzzled over is how to support managing multiple pages from one Facebook app? Anyone know the answer to this, or do you need to create anew app and get permission for every page?