# 15003: Call Progress: Warning Response to Callback URL

Log Type: APPLICATION

Log Level: WARNING

## Description

Got an HTTP warning in response to the callback URL.

### Possible causes

* Your application returned a 4xx or 5xx HTTP response to Twilio.

### Possible solutions

Ensure your application responds to callbacks with:

* `200 OK`
* `Content-Type`: text/xml
* Valid TwiML

Or respond with 204 No Content and an empty response body.