The Hybrid Admin

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The Login Loop: Resolving Teams Error 0xCAA90006

The Login Loop: Resolving Teams Error 0xCAA90006

If you are trapped in a cycle where Teams asks for your password, seems to accept it, and then immediately asks again, you are likely dealing with Error 0xCAA90006. This is a “Modern Authentication” failure. It usually means the client sent a request for an authorization token, but the server sent back an “Invalid Request” because the data in the handshake was malformed or expired.

When this happens, Teams doesn’t know how to move forward, so it simply resets the login process, creating the dreaded infinite loop.

Step 1: Clear the Work or School Account “Bridge”

This error often stems from a mismatch between your Windows identity and the Teams app identity. Refreshing this connection is the most reliable way to break the loop.

  1. Open Windows Settings (Press Win + I).
  2. Navigate to Accounts > Access work or school.
  3. Click on your work account and select Disconnect. (Note: This will log you out of other Office apps briefly).
  4. Restart your computer.
  5. Go back to the same menu and click Connect to re-add your account.

Step 2: Wipe the Identity Cache (The “Local” Fix)

Teams stores “Identity” fragments in a specific folder that isn’t always cleared during a standard uninstall. If these files are corrupt, the loop will persist.

  1. Close Teams completely via the Task Manager (Ctrl + Shift + Esc).
  2. Press Windows Key + R, type %localappdata%\Microsoft\IdentityCache, and hit Enter.
  3. Select all folders inside (usually numbered folders) and Delete them.
  4. Restart Teams. It will be forced to generate a brand-new identity token from scratch.

Step 3: Update the Web Account Manager (WAM)

The 0xCAA90006 error can occur if the Windows component that “brokers” your login is outdated or has a registration glitch.

  1. Right-click the Start button and select PowerShell (Admin).
  2. Run the following command to re-register the Microsoft AAD plugin:Add-AppxPackage -Register "$Env:SystemRoot\SystemApps\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\AppxManifest.xml" -DisableDevelopmentMode -ForceApplicationShutdown
  3. Once the command finishes, restart your device.

Step 4: Check for Conflicting Browser Credentials

Teams uses an embedded browser for its login screen. If you have a different “personal” Microsoft account signed into your default browser (Chrome or Edge), it can sometimes interfere with the “Work” authorization.

  1. Open your browser and go to portal.office.com.
  2. Sign out of all accounts.
  3. Clear your browser’s Cookies and Cache.
  4. Attempt to log into the Teams desktop app again.

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