# Authentication

> Fix 401 Unauthorized and failed token requests: OAuth off, no authorization header, grant type not allowed, invalid secret, redirect URI, lost admin password.

- **Product:** DS Server
- **Section:** Documentation
- **Kind:** Topic
- **Path:** DS Server > Troubleshooting > Authentication
- **Web URL:** https://docs.textcontrol.com/ds-server/troubleshooting/authentication/
- **LLMs URL:** https://docs.textcontrol.com/ds-server/troubleshooting/authentication/llms.txt
- **LLMs-Full URL:** https://docs.textcontrol.com/ds-server/troubleshooting/authentication/llms-full.txt

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## On This Page

- [Requests Work Without a Token](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#requests-work-without-a-token)
- [Requests Return 401 Unauthorized](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#requests-return-401-unauthorized)
- [The Token Request Reports a Missing Authorization Header](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#the-token-request-reports-a-missing-authorization-header)
- [The Token Request Says the Grant Type Isn't Allowed](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#the-token-request-says-the-grant-type-isn-t-allowed)
- [The Token Request Reports an Invalid Client Secret](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#the-token-request-reports-an-invalid-client-secret)
- [The Redirect URI Doesn't Match](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#the-redirect-uri-doesn-t-match)
- [The Admin Password Is Lost](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#the-admin-password-is-lost)
- [The Log Mentions Authentication Servers](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#the-log-mentions-authentication-servers)
- [Related Pages](https://docs.textcontrol.com/ds-server/troubleshooting/authentication/#related-pages)

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## Nearby

- **Previous:** [Installation](https://docs.textcontrol.com/ds-server/troubleshooting/installation/llms.txt)
- **Next:** [Document Editor and Viewer](https://docs.textcontrol.com/ds-server/troubleshooting/editor-viewer/llms.txt)