# 21655: The ContentSid is Invalid

Log Type: APPLICATION

Log Level: ERROR

## Description

This error means the `ContentSid` in your message request is not a valid Content Template SID for the message you are sending. Use a valid Content Template SID that matches the `HX` pattern and belongs to the same account that is creating the Message resource.

### Possible causes

* The `ContentSid` value has a typo, is incomplete, or does not match the required `^HX[0-9a-fA-F]{32}$` format.
* The template was deleted, so the SID no longer points to an active Content Template.
* The template belongs to a different account or subaccount than the one used to create the message. A Content Sid can only be used by one Twilio account SID, and the Message resource is created under the account in your request.

### Possible solutions

* Copy the `ContentSid` directly from the Content Template Builder or from the Content API response. Confirm that it starts with `HX` and is 34 characters long.
* Verify that the template still exists by fetching it with `GET /v1/Content/{ContentSid}` or by listing templates with `GET /v1/Content`. If the template was deleted, create a new template and update your request to use the new SID.
* Send the message from the same account or subaccount that owns the template. If you authenticate the request with a different account, use a `ContentSid` created under that account instead.

#### Additional resources

* [Send templates created with the Content Template Builder](/docs/content/send-templates-created-with-the-content-template-builder)
* [Content API public endpoints](/docs/content/content-api-resources)
* [FAQs and Troubleshooting](/docs/content/faqs-and-troubleshooting)