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CAA20002 Severity: High

Could not connect to Microsoft servers

Teams reports CAA20002 during sign-in. Usually caused by a blocked network, outdated TLS settings, or a corrupted token cache.

Last verified:

Affected systems

windows macos

Symptoms

  • Sign-in fails with CAA20002
  • Teams hangs on the login screen
  • Other Microsoft services in the browser keep working

Possible causes

  • Cache full of expired auth tokens
  • Active VPN or proxy blocks login.microsoftonline.com
  • TLS 1.2 disabled on the machine
  • Wrong date or timezone setting

Solutions

1.Clear the Teams cache fully

  1. Kill all Teams processes via Task Manager (Ctrl + Shift + Esc).

  2. Delete the cache folder.

    %appdata%\Microsoft\Teams

  3. Relaunch Teams and sign in fresh.

2.Disable VPN and test proxy

  1. Disconnect the VPN tunnel and try signing in without it.

  2. If your company uses a proxy, verify login.microsoftonline.com and teams.microsoft.com are reachable.

  3. Ask IT to allowlist the Microsoft 365 endpoints if needed.

3.Enable TLS 1.2 on Windows

  1. Open 'Internet Options' (inetcpl.cpl) via Run.

  2. Advanced tab, make sure 'Use TLS 1.2' is enabled.

  3. Apply and reboot.

4.Verify date and time

  1. Open Settings, Time and Language.

  2. Enable automatic time and timezone sync.

  3. Click 'Sync now'.

CAA20002 is almost always a client problem, not a server outage. If your account works fine on office.com in a browser, the cache reset fixes more than 80 percent of cases.

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