Webhook URL Verification fails with Heroku

Question

### Pre condition, Condition to reproduce
I implemented a bot by Django, and I have tested it with ngrok. It works without any problem and I can send the message to the bot on Line. However, after I uploaded the project to Github and deploy it on Heroku, even though the deployment is success, I can't make it work properly.

### Issue/ Error Message details
After I clicking the "verify" button at Webhook settings, I always get error message:

The webhook returned an HTTP status code other than 200.(503 Service Unavailable)
Confirm that your bot server returns status code 200 in response to the HTTP POST request sent from the LINE Platform. For more information, see Response in the Messaging API Reference.

I am not sure what happened, and I have also check my webhook url https://PROJECTNAME.herokuapp.com/callback by SSL checker: https://www.sslshopper.com/ and nothing wrong. 

### Accompanying respective source code


### Resolution Tried


### Reference information (Version / Platform/ environment)
Python 3.7
Django
Heroku

intact · Answer

Webhook is a means to receive the result after sending a message.
I understood that the implemented bot succeeded in sending message, but it would be better to separately check whether it is possible to connect to the implemented webhook's endpoint (https://PROJECTNAME.herokuapp.com/callback).
The simplest way is to check what happens when you call the endpoint of the webhook directly from your PC.

マラカ サンジーワ · Answer

did you configure the variables in heroku app?
you should configure the following from heroku config vars.
channel access token 
channel secret

Q&A

Webhook URL Verification fails with Heroku

Pre condition, Condition to reproduce

Issue/ Error Message details

Accompanying respective source code

Resolution Tried

Reference information (Version / Platform/ environment)