When Microsoft Teams shows 0xCAA5001C on Windows, the desktop app usually breaks before it completes the Microsoft Entra sign-in flow. Microsoft documents this code as a token broker operation failed condition tied to the Windows authentication layer and the Microsoft.AAD.BrokerPlugin path, not to Teams chat data itself. [✅Source-1]
That changes the fix order. Teams on Windows uses modern authentication and Web Account Manager, so a desktop-only failure often points to a local identity problem: stale account binding, broken cache, unhealthy device registration, or broker permissions inside the user profile. Often, the app is only the messenger. [✅Source-2]
Desktop app fails, web worksEvent Viewer shows ID 1098AAD/Operational logWAM or BrokerPlugin path
Start with the Windows identity stack first. A tenant-wide outage is possible, but this code usually rewards local troubleshooting before anything else.
Table of Contents
What 0xCAA5001C Usually Means
On a Windows Teams desktop sign-in failure, 0xCAA5001C usually means the app could not finish a brokered sign-in request. Engineers often compare this behavior with other documented Microsoft Teams sign-in error codes to confirm whether the failure belongs to the Windows identity layer rather than the Teams client itself. The visible symptom is Teams. The broken layer is often lower: Windows account state, WAM, device registration, or the broker plugin registry path. If the same machine also shows trouble in other Microsoft 365 sign-ins, that pattern gets even stronger.
One detail gets missed a lot: Microsoft’s dedicated article for this code lives under Windows Client, not under Teams. That is why many Teams-only articles stay too high-level. They stop at cache clearing and reinstalling. Useful, yes. Not always enough. When this code keeps returning, you have to inspect the Windows identity plumbing underneath the Teams window.
| What You See | What It Usually Points To | Best Next Move |
|---|---|---|
| Teams on the web signs in, desktop app fails | Local client, WAM, or profile-bound auth issue | Clear cache, sign out, refresh account binding |
| Event Viewer logs Event ID 1098 in AAD/Operational | Broker plugin ownership or permission problem | Inspect the PSR registry path and inheritance |
dsregcmd /status shows DeviceAuthStatus : FAILED | Device registration or system-context connectivity problem | Fix device state before chasing Teams itself |
| License was changed recently | Access has not settled yet | Verify the assigned Teams license and allow time for propagation |
How To Verify the Failure Before You Change Anything
Open Event Viewer and check the Microsoft-Windows-AAD/Operational log. If you see Event ID 1098 with 0xCAA5001C, you are no longer guessing. Hidden behind Teams, the broker layer is reporting the same code Microsoft documents in the Windows identity stack.
Then run dsregcmd /status in an elevated Command Prompt while signed in as the affected domain user. Focus on AzureAdJoined, DomainJoined, and DeviceAuthStatus. A healthy joined device should show a valid join state and DeviceAuthStatus : SUCCESS. If you get FAILED or FAILED.ERROR, pause the Teams-only fix path and repair device trust first. [✅Source-3]
If you want deeper evidence, Microsoft’s DSRegTool PowerShell performs more than 50 tests and can collect AAD broker, Kerberos, WebAuth, system, and network traces in one pass. For stubborn 0xCAA5001C loops, that shortens the time to a clean root cause. [✅Source-4]
Fix the Problem in the Right Order
Close Teams and Clear the Local Cache
- Quit Teams fully from the system tray.
- If you use Classic Teams, remove the contents of
%appdata%\Microsoft\Teams. - If you use New Teams, clear
%userprofile%\appdata\local\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\MSTeams. - Open Teams again and expect the first launch to take a little longer while the cache rebuilds.
This step matters because stale token artifacts, broken local settings, and cached account state can survive normal restarts. Microsoft documents separate cache locations for classic and new Teams, and notes that the first restart may be slower after the rebuild. [✅Source-5]
Sign Out of Teams and Refresh the Account Binding
Sign out inside Teams first. Then sign back in with the affected work account. That sounds basic, but it clears the app-side token relationship before you touch Windows account state. Keep the move clean: one account, one fresh sign-in, no switching during the test. [✅Source-6]
If the machine shows the wrong or stale Work or School credential in Windows, disconnect it from Settings > Accounts > Access work or school, restart, and add the correct account again. Microsoft also notes that some antivirus, proxy, firewall, or VPN setups can block Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy, so test without those controls in the path if your environment allows it. [✅Source-7]
Check Device State Before You Go Any Further
Look for these fields in dsregcmd /status:
- AzureAdJoined and DomainJoined to confirm the expected join type
- DeviceAuthStatus to see whether the device is healthy in Microsoft Entra ID
- Thumbprint and DeviceCertificateValidity to spot certificate trouble
- TpmProtected and KeyProvider when you suspect local key-storage problems
If device trust is broken, Teams keeps tripping over the same wall. Fix that first.
Update Teams, Run the Sign-In Diagnostic, and Reinstall if Needed
For admins, Microsoft provides a Teams Sign-in diagnostic and also points to the Remote Connectivity Analyzer test. If that does not surface the fault, Microsoft’s manual path is clear: check for the latest Teams update, then reinstall the client if the sign-in error persists. The same article also notes platform limits for those diagnostic tools, which matters in special cloud environments. [✅Source-8]
Repair the Broker Plugin Permission Issue
If Event Viewer keeps logging 1098 with 0xCAA5001C, move to the broker permission repair. This is the fix many short articles skip. On an affected profile, inspect these registry paths:
HKEY_CURRENT_USER\Software\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\AppModel\SystemAppData\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\PSR
HKEY_USERS\<User-SID>\Software\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\AppModel\SystemAppData\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\PSRWhat you want to see is simple, though the path is not: owner set to SYSTEM, inheritance enabled, and the expected full-control entries for SYSTEM, the affected user, and Administrators. Microsoft also calls out the app package SID with Query Value on the key itself. Match the SID from Event ID 1098 to the user path under HKEY_USERS. If one key is wrong, fixing inheritance often fixes both on a single-user device.
Use this path only when the evidence matches. 0xCAA5001C plus Event ID 1098 is the point where this repair becomes rational. Without that, random registry edits just add noise.
Admin Checks That Are Easy to Miss
License Assignment and Timing
Do not skip the license layer. Microsoft states that, except for anonymous meeting join, each user needs a Teams license to use Teams, and disabling a Teams SKU can take about 24 hours to take effect. If access changed today, a clean local client can still look broken until licensing settles. [✅Source-9]
Windows Version and Sign-In Design
Microsoft recommends Windows 10 version 1903 or later for the best Teams single sign-on experience. Older or poorly aligned device states can still work, but they tend to break more often around silent sign-in, MFA handoff, and account prefill behavior. If this machine is old, half-managed, or recently rejoined, note it early and treat that as part of the incident.
What Not To Do
Do not try to “fix” 0xCAA5001C by turning off WAM or ADAL. Microsoft explicitly says that disabling those sign-in components is unsupported and may adversely affect the environment. On Windows, modern sign-in behavior is designed around WAM, and forcing legacy behavior usually trades one broken sign-in for a wider identity mess. [✅Source-10]
FAQ
Does 0xCAA5001C always mean Teams itself is broken?
No. In many Windows cases, Teams is only where the error surfaces. The deeper issue is often in the local sign-in broker, account binding, or device registration path. If the browser version opens and the desktop app does not, that pattern leans even more toward a local Windows identity problem.
Can I keep working in the browser while I fix the desktop app?
Yes. Microsoft’s Teams support guidance explicitly suggests trying the web version at https://teams.microsoft.com when the desktop app is not reconnecting. That is useful both as a temporary workaround and as a scope test. [✅Source-11]
Which cache path should I clear for New Teams?
Use %userprofile%\appdata\local\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\MSTeams. For Classic Teams, use %appdata%\Microsoft\Teams. Clearing the wrong path wastes time and leaves the real cache intact.
When I reinstall Teams on Windows, do I need to remove more than one item?
Yes. Microsoft’s uninstall instructions say a full Windows removal requires uninstalling both Microsoft Teams and Teams Machine-Wide Installer. If you remove only one, the old installation state can linger. [✅Source-12]
What tells me this is a device-trust issue and not just a bad cache?
If dsregcmd /status shows an unhealthy join state or DeviceAuthStatus : FAILED, treat the machine as a device registration problem first. A clean cache cannot repair broken trust with Microsoft Entra ID.
When should I stop and hand the case to IT?
Escalate when any of these are true: Event ID 1098 keeps returning after cache clearing, the broker registry path has wrong ownership or broken inheritance, dsregcmd shows failed device auth, the user’s license changed recently, or the environment uses proxy, VPN, firewall, or conditional access rules that the endpoint user cannot safely modify.