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As mentioned by Igor, a WebHook can become blacklisted when the endpoint is unresponsive.

For me, this can happen when I'm doing development on my laptop and I shutdown the service and/or laptop. To deal with this, I built a small command line app that will list subscriptions and "recreate" them with the same endpoint if they become blacklisted (create a new one and delete the old one) so you can move forward to development instead of waiting for a webhook to get off the blacklist. You can get this here:

https://github.com/grokify/rchooks

Hi Jayakumar,

Yes, we have blacklisting rules for Webhooks, since Webhook subscription has pretty long expiration period (up to 15 years).

There are several requirements to your Webhook URL:

1. It's available on the Internet
2. It can respond within 3000 milliseconds 

... and some other, specified in
http://ringcentral-api-docs.readthedocs.io/en/latest/notifications_webhooks/

If WebHook url doesn't meet above requirements during 10 minutes subscription became blacklisted. Subscription became Active during reconcilation (every 15 minutes) if WebHook url became valid.

blacklistedData is available for blacklisted WebHook subscriptions, you can retrieve it as part of Subscription List API response, see https://developers.ringcentral.com/api-docs/latest/index.html#!#RefGetSubscriptionList

E.g.

"blacklistedData": {
"reason": "Webhook responses with code: [404], reason: [Not Found]",
"blacklistedAt": "2018-08-03T12:44:03.105Z" 
}

Thanks,
Igor