teams Code caa20003

How to Fix Microsoft Teams Error caa20003

Diagnostic Procedures

  • 1 Understand the cause of Teams login error caa20003
  • 2 Clear Teams client cache databases on Windows
  • 3 Clear Teams client cache databases on macOS
  • 4 Disconnect and reconnect Work or School accounts in Windows Settings
  • 5 Resolve cached Microsoft credentials from macOS Keychain
  • 6 Summary checklist for error caa20003

How to Fix Microsoft Teams Error caa20003

Failing to sign in to Microsoft Teams and receiving Error Code caa20003 indicates that your local client application failed to complete the secure OAuth authentication handshake with Microsoft 365. This sign-in loop prevents access, typically displaying the message “We’re sorry—we’ve run into an issue.”

This guide walks you through purging corrupted Teams cache directories, resetting operating system credential bindings, and restoring secure server connections on both Windows and macOS.

1. What Causes Teams Error caa20003?

Login handshake failures are caused by local system states and server policies:

  • Stale Security Tokens: Microsoft Teams caches authentication tokens. If your password was changed, or if a token expires, the client may fail to renew the lease and get stuck in a handshake loop.
  • Corrupted Local Client Cache: Cached JSON databases and cookies inside Teams application directories become corrupted, blocking authentication prompts.
  • Workplace Join Account Conflict: Local Windows user logins mapped to “Access Work or School” accounts conflict with Entra ID sign-in tokens.
  • Time Out of Sync: The local computer clock diverges by more than 5 minutes from the Microsoft authentication server clock, causing security token validation to fail.

2. Clear Teams Client App Caches

Purging the cache forces Teams to perform a clean authentication handshake.

A. On Windows (New Microsoft Teams V2)

  1. Close Microsoft Teams completely (right-click the Teams icon in the system tray and select Quit).
  2. Press Windows Key + R to open the Run dialog.
  3. Paste the path below and press Enter: 
    %localappdata%\Packages\MSTeams_8wekyb3d8bbwe
  4. Delete all files and folders inside this directory.
  5. Relaunch Teams.

B. On macOS (New Microsoft Teams V2)

  1. Quit Microsoft Teams (press Cmd + Q).
  2. Open Terminal (via Spotlight search).
  3. Execute the following commands to delete cached folders: 
    rm -rf ~/Library/Group\ Containers/UBF8T346G9.com.microsoft.teams
rm -rf ~/Library/Containers/com.microsoft.teams2
  4. Relaunch Teams.

3. Disconnect & Reconnect Work/School Accounts (Windows)

If clearing the cache fails, Windows’ central credential manager may be passing stale tokens:

  1. Press Windows Key + I to open Settings.
  2. Navigate to Accounts → Access work or school.
  3. Select your work or school account and click Disconnect (confirming when prompted).
  4. Reboot your computer.
  5. Go back to Access work or school, click Connect, and re-enter your Microsoft 365 email and password.
  6. Launch Teams to sign back in.

4. Reset Cached Credentials on macOS

If Teams loops on macOS, delete the Office and Teams identity entries:

  1. Quit Microsoft Teams.
  2. Open Keychain Access via Spotlight.
  3. In the top-right search box, search for Microsoft Teams and Microsoft Office.
  4. Right-click and delete all keys matching:
    • Microsoft Teams Identities Cache
    • Microsoft Office Identities Settings
    • com.microsoft.teams.adalsession
  5. Restart your Mac and launch Teams to authenticate.

5. Summary Quick Reference Checklist

Troubleshooting TargetTarget Command / PathExpected Outcome
Windows Cache Clear%localappdata%\Packages\MSTeams_8wekyb3d8bbweDeletes corrupt JSON databases and tokens.
macOS Cache Clearrm -rf ~/Library/Containers/com.microsoft.teams2Force-resets Teams V2 client settings.
Credential ManagerDisconnect under Windows “Access work or school” settingsRenews central Workplace Join tokens.
Keychain ResetPurge com.microsoft.teams.adalsession in KeychainForces Mac to request a new browser login.
Time Sync CheckRight-click clock → click “Sync Now”Prevents security handshake time-skew errors.