# invalid_client

> OAuth (Sign in with Tickwire): the client could not be identified or authenticated.

Source: https://tickwire.io/docs/errors/invalid_client/

HTTP 400, 401.

**Likely causes:**

- Unknown client_id: register the app first (DCR) or use a valid client metadata document URL.
- Wrong or missing client secret for a confidential client, or a secret sent by a public client.
- The client metadata document could not be loaded or is invalid.
- The app sent a token exchange request with credentials we do not accept.

**What to do:** Check the client registration and its credentials; re-register if needed.

**Retry:** No. The same request gets the same answer; change something first.

Listed under [Sign in with Tickwire (OAuth)](https://tickwire.io/docs/errors/#sign-in-with-tickwire-oauth) in [Errors](https://tickwire.io/docs/errors/). Send the error's `requestId` to support and we can find the request.