For Microsoft Teams Error Code 0xCAA50021, the first place to inspect is the sign-in layer, not chats, channels, or meeting data. On Windows, Teams relies on modern authentication, single sign-on, and the system account stack that feeds Microsoft apps. When that handoff breaks, Teams can stop at 0xCAA50021 even though the account itself is still valid. [✅Source-1]
Table of Contents
What Usually Matters Most
If Teams on the web works and the desktop app fails, the fault is usually local to Windows sign-in state, stored credentials, local Teams cache, or device registration. If Outlook or OneDrive also fail on the same PC, think wider: the shared Microsoft sign-in stack is the better place to look.
What 0xCAA50021 Usually Means
0xCAA50021 is best treated as a Windows and Microsoft 365 authentication-state problem. Microsoft’s own remediation for this code centers on cached Office credentials, the Access Work or School account binding, the Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy process, license assignment, Microsoft Entra device registration, and leaving or rejoining the device to Entra when the join state is broken. That is why a pure “clear Teams and retry” approach often helps only part of the time. [✅Source-2]
- Authentication broker: Windows passes tokens through components that Teams and other Microsoft apps reuse.
- Account binding: The wrong work or school account in Windows can keep feeding the wrong token path.
- Device registration: A stale or failed join state can stop desktop sign-in before Teams fully opens.
- License state: A valid account still needs the right Teams entitlement.
Where to Look First
Desktop Fails, Web Works
Focus on local cache, saved credentials, the Windows work account, and device join state.
Teams, Outlook, and OneDrive Fail
Treat it as a shared Microsoft sign-in problem. Check WAM, BrokerPlugin, and Entra device registration first.
Web and Desktop Both Fail
Move quickly to license, tenant policy, Microsoft 365 diagnostics, and sign-in testing from the admin side.
| Observed Pattern | Most Likely Layer | Best First Move |
|---|---|---|
| Only one Windows profile shows 0xCAA50021 | Local sign-in cache or account binding | Remove saved credentials and clear Teams cache |
| Teams opens on the web but not on desktop | Desktop token path, WAM, or device registration | Check Access Work or School and run dsregcmd /status |
| Teams plus other Microsoft apps fail | Shared authentication stack | Check BrokerPlugin, device join, and admin license state |
| Issue returns after password or policy changes | Old token state | Sign out, refresh local account state, then update or reinstall if needed |
Fix Order That Saves the Most Time
- Test the same account in Teams on the web.
- Remove Windows credentials tied to Microsoft 365 and disconnect the wrong work or school account if Windows is holding one.
- Clear the Teams desktop cache.
- Check the Teams version and run an update.
- Do a clean uninstall if the desktop app still loops on sign-in.
- Run dsregcmd /status and verify the device join state.
- For managed tenants, have an admin verify license, device registration settings, and the Teams sign-in diagnostic.
Sign Out and Compare Desktop With Web
Open teams.microsoft.com with the same work or school account. If the browser session signs in cleanly while the desktop app keeps throwing 0xCAA50021, spend your time on the Windows client path, not the tenant itself. That comparison removes guesswork fast. [✅Source-3]
Remove Saved Office Credentials and Disconnect the Wrong Work or School Account
- Open Credential Manager.
- Select Windows Credentials.
- Remove entries for MicrosoftOffice16 if they exist.
- Go to Settings > Accounts > Access Work or School.
- If Windows shows the Microsoft 365 account you use for Office or Teams, but it is not the Windows sign-in account, disconnect it.
- Restart the PC and test Teams again.
This step matters because stale cached credentials and a mismatched Windows work account can keep pushing Teams into the same failed token route. When that is the root cause, clearing the cache alone often leaves the problem half-fixed.
Clear Teams Cache on Windows
- Quit Teams from the taskbar.
- Open File Explorer.
- Go to
%appdata%\Microsoft\Teams. - Delete the contents of that folder.
- Start Teams and sign in again.
Microsoft notes that this removes local Teams cache data such as thumbnails, web cache, local message history, and other local app data, while leaving the installed app itself in place. It is the right move when desktop state looks corrupted but you do not yet want a full reinstall.
Update Teams and Confirm the Installed Version
- In Teams, open Settings and More.
- Select Update and Restart Teams if it appears.
- Then go to Settings > About Teams.
- Check the Version field and confirm whether Teams says it is current.
Teams auto-updates when an update is available and the app is idle, but a stuck client is not always on the latest build. Check the version before spending time on heavier repair steps. [✅Source-4]
If you want a second confirmation point, About Teams is where Microsoft says to verify whether the installed build is current or whether Update Now is available. [✅Source-5]
Reinstall Teams Cleanly
When the sign-in loop survives credential cleanup, cache removal, and an update check, move to a clean reinstall. On Windows, Microsoft says to uninstall both Microsoft Teams and Teams Machine-Wide Installer. Leaving the machine-wide installer behind can make the repair look complete while old deployment state still remains in the background. [✅Source-6]
Check BrokerPlugin, VPN, Proxy, and Security Tools
One detail many short fix pages skip: Microsoft names the Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy process directly in its 0xCAA50021 troubleshooting. If antivirus, a proxy, a firewall, or a VPN path interferes with that process, Teams can fail before the desktop token exchange settles. That is why this error can feel random on one network and perfectly normal on another.
If you are on a managed device, test in a controlled order: turn off the VPN, retry Teams, then have IT review proxy or firewall handling for Microsoft sign-in traffic. If the account works on the web but breaks on the Windows app, this section deserves real attention.
Token Paths Microsoft Calls Out
%LOCALAPPDATA%\Packages\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\AC\TokenBroker\Accounts %LOCALAPPDATA%\Packages\Microsoft.Windows.CloudExperienceHost_cw5n1h2txyewy\AC\TokenBroker\Accounts
Microsoft’s 0xCAA50021 article points to these locations when BrokerPlugin data needs to be cleared as part of repair.
Check Device Registration With dsregcmd
When 0xCAA50021 stays alive after local cleanup, check whether the PC is still joined to Microsoft Entra the way Windows thinks it is. Microsoft’s troubleshooting flow uses dsregcmd for exactly this reason. The output tells you whether the machine is AzureAdJoined, and that single line often separates a normal Teams repair from an admin-level identity repair. [✅Source-7]
dsregcmd /status
Look for AzureAdJoined : YES or AzureAdJoined : NO. If the value is NO on a device that should be joined, Teams can keep failing because the local device trust is not lined up with the account path anymore.
dsregcmd /leave Restart Windows dsregcmd /status dsregcmd /join
Use the leave and join path with care on managed devices. In many organizations, IT should drive this step so the device returns with the right policy set and the right registration record.
Admin Checks That Commonly Finish the Fix
If a normal user already cleared the local state and the web client still looks different from the desktop client, the next wins usually come from the admin side. Microsoft states that each user needs a Teams license to use Teams, apart from anonymous meeting join. The same Microsoft guidance also documents the Teams service plan identifier TEAMS1 for license work in PowerShell. [✅Source-8]
- Confirm the affected user still has a valid Teams-enabled license.
- If the license already exists, remove and re-save the assignment from Licenses and Apps.
- In Microsoft Entra device settings, confirm that users may join and register devices if your sign-in model depends on it.
- Run the Teams Sign-in diagnostic from the Microsoft 365 admin center.
- Run the Microsoft Remote Connectivity Analyzer Teams sign-in test for the affected account.
That admin path matters because 0xCAA50021 can look like a local desktop fault while the real blocker sits in license state, tenant sign-in policy, or device registration permissions. Many administrators also compare the issue with other documented Microsoft Teams sign-in error codes to confirm whether the failure is tied to authentication flow, device join state, or policy configuration. Microsoft’s Teams sign-in article points admins to both the built-in diagnostic and the Remote Connectivity Analyzer for this reason. [✅Source-9]
| Admin Check | What to Verify | Why It Changes the Outcome |
|---|---|---|
| License | Teams entitlement is present for the user | No valid Teams license means desktop sign-in cannot complete normally |
| Device Settings | Users may join and register devices where required | Broken or blocked registration can feed 0xCAA50021 on Windows |
| Diagnostics | Run Tests: Teams Sign-in and Remote Connectivity Analyzer | Confirms whether the account meets Teams sign-in requirements |
| Client Health | User is on a current Teams build | Old local state can keep stale sign-in behavior alive |
Useful Technical Data
- Teams cache path on Windows:
%appdata%\Microsoft\Teams - Broker process name:
Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy - Device status command:
dsregcmd /status - Leave current Entra join:
dsregcmd /leave - Join Entra again:
dsregcmd /join - Teams license service plan ID for PowerShell work:
TEAMS1 - Where to confirm version in Teams:
Settings > About Teams
A Good Reading of the Pattern
When web Teams works, desktop Teams fails, and other Microsoft apps show odd sign-in behavior on the same PC, that pattern strongly favors Windows account state, BrokerPlugin, or device registration over a normal Teams app bug. Seen this way, the repair order becomes much clearer. And faster.
FAQ
Does Error Code 0xCAA50021 Mean My Teams Password Is Wrong?
Not by itself. This code often appears when desktop authentication state is broken even though the account password is still valid. If the same account signs in on the web, focus first on local credentials, Teams cache, and device registration.
Why Does Teams on the Web Work While the Desktop App Fails?
That pattern usually means the tenant and account are mostly fine, while the Windows client path is not. In practice, the common culprits are saved Office credentials, the wrong account under Access Work or School, broken BrokerPlugin data, or an invalid Entra join state.
Should I Clear the Cache Before Reinstalling Teams?
Yes. A cache clear is faster, cleaner, and often enough. Move to a full reinstall when credential cleanup, cache removal, and an update check fail to change the sign-in behavior.
What Should I Check in dsregcmd /status?
Look first for AzureAdJoined. A device that should be joined but shows NO can keep Teams from finishing the desktop sign-in flow. In managed environments, let IT handle the leave and rejoin steps.
When Should an Admin Step In?
Bring in an admin when the browser and desktop behave differently after local repair, when Outlook or OneDrive also fail, when license state looks unclear, or when device registration does not return to normal.