Fix Microsoft Teams Error CAA20003 Sign-In Loop

Microsoft Teams shows error CAA20003 and you're stuck in a sign-in loop. You enter your credentials, Teams thinks about it, then asks for credentials again. Or it shows a blank white screen and eventually throws the CAA20003 error. This blocks access to chat, meetings, and everything else in Teams.

The Fix

Close Teams completely and delete its cache folder:

# Kill all Teams processes Get-Process -Name "teams" -ErrorAction SilentlyContinue | Stop-Process -Force # Delete Teams cache (Classic Teams) Remove-Item -Path "$env:APPDATA\Microsoft\Teams" -Recurse -Force -ErrorAction SilentlyContinue # Delete Teams cache (New Teams) Remove-Item -Path "$env:LOCALAPPDATA\Packages\MSTeams_*" -Recurse -Force -ErrorAction SilentlyContinue

Restart Teams. It will recreate the cache folder and prompt you to sign in fresh.

Clear Credential Manager

If the cache clear doesn't work, remove stored Teams credentials:

# List Microsoft credentials cmdkey /list | Select-String "Microsoft" # Delete Teams-related credentials cmdkey /delete:MicrosoftTeams cmdkey /delete:LegacyGeneric:target=MicrosoftTeams cmdkey /delete:"MicrosoftAccount:user=youremail@domain.com"

Or open Credential Manager from Control Panel, go to Windows Credentials, and manually remove anything containing "Teams" or "Office".

If That Doesn't Work

Sign out of all Microsoft accounts in Windows:

Open Settings > Accounts > Email & accounts
Remove any Work or school accounts listed
Re-add your account
Try Teams again

For persistent issues, try the web version at https://teams.microsoft.com to verify your account works, then troubleshoot the desktop app separately.

CAA20003 is a generic authentication failure code. It usually means cached credentials or tokens are corrupted or expired. The sign-in loop happens because Teams keeps trying the bad cached data instead of prompting for fresh credentials.