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Hi, we are using server which is live and still getting  'SUB-521', message: 'WebHook is not reachable'. but thing is that if we try after 5 seconds it works perfectly fine.

Thank you all for your prompt response. Today i am able to create subscription successfully in the same setup. What i just did is uninstall the ngrok and reinstalled and tried out :-)

I have this application (written in Node.js) which shows how to setup Webhooks and receive the event notifications from them properly.

https://github.com/bdeanindy/ringcentral-webhook-basics

Additionally, this has a one-button Heroku deployment (which makes it really easy to get started using/testing with this quickly).

I am too facing similar problem. 

1. The request is coming through successfully, via the internet.
2. Using ngrok for local tunnel
3. From the server perspective, the response is around ~300 ms each time.
4. I am indeed capturing and returning the 'Validation-Token'.(200 status)

Getting below response

{

  "errorCode" : "SUB-521",

  "message" : "WebHook is not reachable",

  "errors" : [ {

    "errorCode" : "SUB-521",

    "message" : "WebHook is not reachable"

  } ]

}

Till last week it was working in the same setup. Today only it is not working. 

Is there any issue in creating a subscription.

Could anyone help me

Thanks

Have you read the doc here: https://github.com/ringcentral/ringcentral-api-docs/blob/master/docs/webhooks.md#create-a-webhook-ur... ?

The webhook URL service must meet the following requirements:

1. is available on the Internet
2. has a TLS / SSL enabled*
3. can respond within 1000 milliseconds
4. will respond with Validation-Token header on subscription

Please make sure that webhook url meets all the requirements above.