teams Code caa20004

How to Fix Microsoft Teams Error caa20004

Diagnostic Procedures

  • 1 Identify the exact meaning of the error code
  • 2 Clear cache or credentials related to the software
  • 3 Check service server status for outages
  • 4 Perform a repair or reset on the desktop client
  • 5 Re-authenticate the connection to sync files

How to Fix Microsoft Teams Error caa20004

If you receive Error Code caa20004 when trying to sign in to Microsoft Teams, it means your login request has been marked as unauthorized by Microsoft Entra ID. This error frequently affects users in federated environments where local identity servers handle authentication.

This guide walks you through resolving the authentication handshake block, updating certificates, and refreshing local configuration databases.

1. Identify the Exact Meaning of the Error Code

Error Code caa20004 translates to an unauthorized request failure.

It is typically triggered by:

  • Missing or Expired Device Certificate: Your organization uses device-based certificate authentication. If the certificate issued to your computer is expired or missing from the personal certificate store, the server denies access.
  • Active Directory Federation Services (AD FS) Failure: The local AD FS server is failing to pass the security assertion token to Entra ID.
  • Security Software Interference: Local firewalls or web proxies are stripping client TLS certificates from the request headers.

Purging local cache databases forces Microsoft Teams to download new security definitions and request a fresh client certificate.

A. Windows PowerShell Steps

  1. Quit Teams.
  2. Open PowerShell and run: 
    Stop-Process -Name "ms-teams" -Force -ErrorAction SilentlyContinue
Remove-Item -Path "$env:LOCALAPPDATA\Packages\MSTeams_8wekyb3d8bbwe\*" -Recurse -Force -ErrorAction SilentlyContinue
  3. Remove stale credentials using the Credential Manager.

B. macOS Terminal Steps

  1. Quit Teams.
  2. In Terminal, run: 
    pkill -9 "Microsoft Teams"
rm -rf ~/Library/Group\ Containers/UBF8T346G9.com.microsoft.teams
rm -rf ~/Library/Containers/com.microsoft.teams2
  3. Open Keychain Access and delete any cached Microsoft Teams security certificates or credentials.

3. Check Service Server Status for Outages

  • Check the Microsoft 365 Service Status Page to rule out global Entra ID issues.
  • If your organization uses a hybrid AD FS setup, check with your network administrator to confirm the AD FS endpoint (adfs.yourdomain.com) is online and answering external queries.

4. Perform a Repair or Reset on the Desktop Client

Corrupt local device registration files can cause authorization failures. Re-registering the Teams package fixes these files.

A. Reset Teams Package (Windows)

Run this command in an elevated PowerShell:

Get-AppxPackage -Name "MSTeams" -AllUsers | Reset-AppxPackage

B. Verify Certificate Store (Windows)

If your organization requires a certificate:

  1. Press Win + R, type certmgr.msc, and press Enter.
  2. Go to Personal → Certificates.
  3. Verify that your user certificate is listed and has not expired. If it is expired, contact your help desk to request a renewal.

5. Re-authenticate the Connection to Sync Files

Rejoining your device to the work domain updates the required security certificates.

A. Reconnect Work Account (Windows)

  1. Go to Settings → Accounts → Access work or school.
  2. Select your account and click Disconnect.
  3. Restart your PC.
  4. Go back to Access work or school, click Connect, and re-authenticate. This automatically downloads new device certificates.
  5. Launch Teams and sign in.

B. Use Private Web Session (Mac & Windows)

  1. Open an Incognito/InPrivate window.
  2. Go to https://teams.microsoft.com.
  3. If you can log in, the issue is isolated to the local desktop client’s access to the certificate store. If the web client also fails, your account is unauthorized on the server side.

6. Summary Quick Reference Checklist

ActionTarget ActionExpected Outcome
Verify Certificate ExpiryCheck certmgr.msc personal certificatesIdentifies expired security credentials.
Disconnect Work AccountSettings -> Accounts -> Access work or schoolTriggers renewal of device certs upon reconnection.
Clear App CachePurge %localappdata%\Packages\MSTeams_8wekyb3d8bbweEliminates corrupt cached handshake tokens.
Verify Proxy SettingsTurn off TLS inspection on proxies/VPNsPrevents certificates from being stripped in transit.
Reset Client AppRun Reset-AppxPackage in PowerShellRestores clean system configurations.