Web hook no longer works for present events while in production.

Is it restored now? Are there any exceptions in the log?

Actually  subscription was not renewed and expired.  I restarted app, created new subscription. 

When renewing subscription my app gets the list of extensions; to do that the app renews access token and gets this error

refresh token:{  "error" : "invalid_grant",
  "errors" : [ {
    "errorCode" : "OAU-202",
    "message" : "Refresh token was not issued for this application"
  } ],
  "error_description" : "Refresh token was not issued for this application"
}


What is application in this context?

I think application is the app you created in developer.ringcentral.com. It seems that you are unable to refresh your access_token. If access_token expired, subscription will expired too(sooner or later).

I am not sure of the root cause without seeing the source code. Could you please post some sample code?

Yes. You are correct. We updated our app and got new app key. So we need to shutdown app and restart using new app key. A bit of a hassle when you upgrade your app.
Thank you for your help.

You are welcome!