The URL couldn't be validated. Callback verification failed with the following errors: HTTP Status Code = 502; HTTP Message = Bad Gateway

[ruby-bot]

my heroku link is not working. I am making Facebook bot in ruby on rails, and this is giving error.
I have attached screenshot of the error, please help me.

[buidairadio]

Have you fixed it yet???

[femo-dev]

Hi, I have the same problem, how did you solve it?

[Baalamurgan]

Hi, I found it the hard way to solve this issue.

1. Make sure you use the correct port and "then" use ngrok (eg.3000). You have to run both ngrok and node simultaneously.
2. Use correct endpoint on both code and on the Callback URL
3. The response is a big json and you have to return req.query["hub.challenge"] as an Integer/Number.