Teams error 401 Unauthorized (expired client secret): Expired client secret

The client secret your bot uses to authenticate has passed its expiry date, so Microsoft Entra refuses to issue tokens. The Entra error reference documents the code as AADSTS7000222 - "InvalidClientSecretExpiredKeysProvided - The provided client secret keys are expired. Create new keys for your app, or consider using certificate credentials for added security."

This is the number one silent killer of production Teams bots. Entra client secrets are created with a maximum lifetime of 24 months, and the portal defaults to less. A bot that shipped and worked flawlessly simply stops replying on the anniversary, with zero warning inside Teams: users see their messages posted normally, the bot never answers, and admins find nothing wrong in the Teams admin center because nothing in Teams is wrong. The only evidence is AADSTS7000222 in your service logs - or in Application Insights if you log adapter errors - at the moment the cached token expired and the refresh failed.

Note what is not wrong: the app registration, the bot registration, the manifest, and the Teams channel are all intact. Creating a new secret value restores service with no reinstallation and no manifest change, because the app ID never changed. The outage window is exactly as long as it takes someone to notice.

{
  "error": "invalid_client",
  "error_description": "AADSTS7000222: The provided client secret keys for app '...' are expired. ...",
  "error_codes": [7000222]
}

Put secret expiry on infrastructure, not on memory: an alert 30 days before expiry (Entra exposes the date via Microsoft Graph), a runbook for rotation, and a startup credential check that pages when token acquisition fails. Rotate by adding the new secret, deploying it everywhere, then deleting the old one - Entra allows multiple concurrent secrets precisely so rotation needs no downtime. Microsoft's own recommendation inside the error string is worth taking: certificate credentials remove the short-expiry treadmill entirely. This failure is cause 2 in Teams bot not responding.