# 13750: Twiml verb not supported by this API version.

Log Level: ERROR

## Description

This error occurs when Twilio starts a new TwiML session with an `apiVersion` that does not support the TwiML your Voice Application returns. The Application resource uses `apiVersion` to start the new TwiML session, and this error directs you to use `2010-04-01` or later.

### Possible causes

* The TwiML Application is configured with `apiVersion` `2008-08-01`, so Twilio starts the call with an older TwiML session version.
* The TwiML returned by your webhook uses a verb that requires `2010-04-01` or later.

### Possible solutions

* Update the Application resource `apiVersion` to `2010-04-01`.
* If you must keep the current API version, return only TwiML verbs supported by that version.
* Confirm the call is reaching the intended Voice URL and that the response is valid TwiML for the selected API version.

#### Additional resources

* [REST API: Applications](/docs/usage/api/applications)
* [TwiML™ for Programmable Voice](/docs/voice/twiml)