# 13807: Client Notification URL Error Response

Log Type: APPLICATION

Log Level: ERROR

## Description

The Client Notification URL returned an error.

### Possible causes

* Your URL is returning 5xx error due to an internal server issue
* Your URL is returning a 400, 401, or 403 due to a server misconfiguration or authentication/authorization issue
* Your URL returned a 404 due to a misconfiguration of your `clientNotificationUrl` in your TwiML or API request
* Your URL returned a 404 because your application could not find a binding for the user receiving the call

### Possible solutions

* Resolve your server errors
* Reconfigure your `clientNotificationUrl` to the correct URL
* Remove the user who has no binding from your call routing
* Return a `200 OK`
* Verify you are using [Client Call Notification Webhook](/docs/voice/sdks/client-call-notification-webhook) correctly