---
page_type: error
code: 51007
message: "51007: Client Connection: Token authentication is rejected"
level: ERROR
---

## Description

## Error - 51007

### Client Connection: Token authentication is rejected by authentication service

### Possible Causes

Authentication service has rejected provided Access Token.

To check whether the Access Token is structurally correct, you can use the tools available at [jwt.io](https://jwt.io/).

For the details of Twilio's specific Access Token implementation including the grant format, see [the documentation](/docs/api/rest/access-tokens).

### Possible Solutions

For further assistance, please reach out to Twilio Support through the [Console](https://console.twilio.com) or [Help Center](https://support.twilio.com).