Title: Error Code 401 “missing required authentication credential” on a weekly basis
Last modified: June 11, 2025

---

# Error Code 401 “missing required authentication credential” on a weekly basis

 *  Resolved [spec](https://wordpress.org/support/users/specwrites/)
 * (@specwrites)
 * [1 year ago](https://wordpress.org/support/topic/error-code-401-missing-required-authentication-credential-on-a-weekly-basis/)
 * Hi there, I successfully installed Post SMTP about a month ago and it generally
   works OK using the Gmail API.
 * However, every single week since installing I am getting error 401:
 * `"error": { "code": 401, "message": "Request is missing required authentication
   credential. Expected OAuth 2 access token, login cookie or other valid authentication
   credential. See https://developers.google.com/identity/sign-in/web/devconsole-
   project.", "errors": [ { "message": "Login Required.", "domain": "global", "reason":"
   required", "location": "Authorization", "locationType": "header" } ], "status":"
   UNAUTHENTICATED", "details": [ { "@type": "type.googleapis.com/google.rpc.ErrorInfo","
   reason": "CREDENTIALS_MISSING", "domain": "googleapis.com", "metadata": { "service":"
   gmail.googleapis.com", "method": "caribou.api.proto.MailboxService.SendMessage"}}]}}`
 * This is fixed fairly quickly by going back to the set-up wizard in WordPress 
   and re-authorizing via Google, but I am getting confused as to why this keeps
   happening so regularly? Does this happen to anyone else? Grateful for any support
   here.

Viewing 3 replies - 1 through 3 (of 3 total)

 *  Plugin Support [M Aqib Khan](https://wordpress.org/support/users/aqibkhan9/)
 * (@aqibkhan9)
 * [12 months ago](https://wordpress.org/support/topic/error-code-401-missing-required-authentication-credential-on-a-weekly-basis/#post-18510464)
 * Hello [@specwrites](https://wordpress.org/support/users/specwrites/) ,
 * We hope this message finds you well.
 * Thank you for reaching out to our Support team. The error message you’re seeing
   is a 401 Unauthorized error from the Gmail API, and it clearly indicates that
   the request is missing the required Client ID & Client Secret (OAuth 2.0 access
   token).
 * changing your Gmail account password will reset all OAuth permissions associated
   with that account. This means that any applications or services that were authorized
   to access your account using OAuth will be disconnected. You will need to reauthorize
   those applications after changing your password. You can utilize our [documentation ](https://postmansmtp.com/documentation/sockets-addons/gmail/)
   for the process.
 * If you encounter any issues with services that use OAuth after changing your 
   password, you may need to log in again or grant permissions anew. Here are the
   [<u>Google Guidelines</u>](https://support.google.com/a/answer/6328616?hl=en)
   as source.
 * Warm regards,
   Support Team – WP Experts
 *  Thread Starter [spec](https://wordpress.org/support/users/specwrites/)
 * (@specwrites)
 * [12 months ago](https://wordpress.org/support/topic/error-code-401-missing-required-authentication-credential-on-a-weekly-basis/#post-18510947)
 * Hi, thanks for the reply, but this issue has nothing to do with the Google account
   password. I haven’t changed it in months. The plugin still regularly gives Error
   401. Could it be an issue with a specific browser, browser extensions, or being
   signed into multiple Google accounts at once? Can you please suggest other possible
   explanations?
 * Best wishes
 *  Plugin Support [M Aqib Khan](https://wordpress.org/support/users/aqibkhan9/)
 * (@aqibkhan9)
 * [10 months ago](https://wordpress.org/support/topic/error-code-401-missing-required-authentication-credential-on-a-weekly-basis/#post-18596799)
 * Hey [@specwrites](https://wordpress.org/support/users/specwrites/) ,
 * If you’re confident the issue isn’t related to a password change, we may need
   to explore other potential causes, such as:
    - A conflict with another plugin or theme
    - Browser or site-level caching
    - Expired or incorrect Google Cloud credentials
 * Warm regards,
   Support Team – WP Experts

Viewing 3 replies - 1 through 3 (of 3 total)

The topic ‘Error Code 401 “missing required authentication credential” on a weekly
basis’ is closed to new replies.

 * ![](https://ps.w.org/post-smtp/assets/icon-128x128.gif?rev=3209655)
 * [Post SMTP – Complete Email Deliverability and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App](https://wordpress.org/plugins/post-smtp/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/post-smtp/#faq)
 * [Support Threads](https://wordpress.org/support/plugin/post-smtp/)
 * [Active Topics](https://wordpress.org/support/plugin/post-smtp/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/post-smtp/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/post-smtp/reviews/)

 * 3 replies
 * 4 participants
 * Last reply from: [M Aqib Khan](https://wordpress.org/support/users/aqibkhan9/)
 * Last activity: [10 months ago](https://wordpress.org/support/topic/error-code-401-missing-required-authentication-credential-on-a-weekly-basis/#post-18596799)
 * Status: resolved