Teams error 401 BotNotRegistered: BotNotRegistered - no registration found

The Connector service could not match the identity your bot presented to any registered Azure Bot resource with the Teams channel enabled. Microsoft's status table documents the code as BotNotRegistered with the message "No registration found for this agent." (earlier versions of the docs and live responses phrase it with "bot" instead of "agent").

This is an identity-plumbing failure, not a permissions one: Teams never evaluated who may talk to whom, because it could not find a bot registration for the app ID inside your token. The three usual shapes are a bot ID that exists in Entra but was never registered as an Azure Bot or Developer Portal bot, a registration that exists but has the Teams channel disabled, and a manifest whose bots[0].botId points at a different app ID than the one your code authenticates with - the classic copy-paste mismatch covered in cause 1 of Teams bot not responding.

{
  "error": {
    "code": "BotNotRegistered",
    "message": "No registration found for this agent."
  }
}

Treat the app ID as a single source of truth injected into both the manifest and the service configuration by your build pipeline, never hand-edited in two places. Keep one bot registration per environment and name them so a mismatch is visible in the portal at a glance. A smoke test that sends one message through the token + send path after each deploy catches registration drift before users do.