# 31007: Twilio Client: Voice JavaScript SDK version not supported

Log Type: APPLICATION

Log Level: ERROR

## Description

Twilio Voice JavaScript SDK 1.x has been shut down. If you are receiving this error, you must upgrade your application to 2.x to restore functionality.

### Possible causes

* You are using Voice JavaScript SDK version 1.x in your application
* You are using Twilio Flex UI version 1.x in your contact center

### Possible solutions

* Upgrade your application to Twilio Voice JavaScript SDK 2.x
* Follow the [Flex migration guide](/docs/flex/developer/ui/migration-guide) to upgrade your Flex instance to UI 2.x