Microsoft Teams: Error Code 0xCAA90056 Fix – Meaning & Steps

Microsoft Teams serves over 320 million monthly active users [✅Source-1], and on Windows the desktop client relies on a brokered sign-in path that uses Primary Refresh Token (PRT), Web Account Manager, and Microsoft Entra token exchange. When Error Code 0xCAA90056 appears, the visible app is Teams, but the break is often lower in that chain. Installed, yes. Authenticated, no. [✅Source-2]

On This Page

What This Error Usually Means

Error Code 0xCAA90056 fits a pattern where Teams sign-in depends on Windows single sign-on, and the token that should refresh in the background does not refresh when needed. Administrators often compare this behavior with other documented Microsoft Teams desktop sign-in error codes to determine whether the failure belongs to the local Windows token chain, device registration state, or the Microsoft Entra authentication layer. Microsoft documents that the PRT is used for silent access to apps such as Teams, that it is valid for 90 days, and that Windows components renew it on a regular cycle while the device is actively used. When that renewal flow stalls, repeated sign-in prompts and desktop app authentication failures become much more likely.

• Windows sign-in state gives the device a base authentication context.
• PRT holds the session state used for single sign-on.
• WAM acts as the Windows token broker for app sign-in.
• Teams requests tokens through that broker path.
• Tenant policy checks still apply, so an account can look fine locally and still fail during token renewal.

What fails first, often, is not Teams itself. It is the token renewal path.

What to Check First

Microsoft’s own troubleshooting flow starts with diagnostics, update state, and the sign-in error shown on screen [✅Source-3].

Fix Steps That Work Most Often

Sign Out Completely

Do not just close the window. Sign out from Teams, close the app, then open it again. That removes the active account state from the Teams app and forces a cleaner sign-in attempt. It is the fastest low-risk reset and should come before reinstalling. [✅Source-4]

Clear the Teams Cache

Cache damage is common after interrupted updates, account switching, or broken sign-in loops. Microsoft documents separate paths for Classic Teams and New Teams. Clear the right one, then restart Teams and allow the app to rebuild local data. Do not skip the restart. [✅Source-5]

Classic Teams path: %appdata%\Microsoft\Teams

New Teams path: %userprofile%\appdata\local\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\MSTeams

Remove Stale Windows Credentials

If the local credential store still holds old Microsoft 365 sign-in data, Teams may keep asking the broker for a token based on stale entries. Open Credential Manager, review saved Windows credentials, remove the ones tied to the affected work or school identity, then restart Windows before testing again. That sequence matters. [✅Source-6]

Check Date, Time, and Time Zone

Wrong clock settings can break secure sign-in even when the username and password are correct. In Windows, turn on Set time automatically and Set time zone automatically, then sync again before reopening Teams. Small drift is enough. [✅Source-7]

Repair or Reset the App

On Windows, open Settings > Apps > Installed apps, find Teams, open Advanced options, then try Repair first and Reset only if repair does not clear the failure. Reset is stronger because it removes app data. Good for broken local state. [✅Source-8]

Check Update State

Teams desktop updates automatically, but Microsoft still tells admins to verify the client is on the latest build when sign-in errors remain. Open the profile menu in Teams and run Check for updates before moving into deeper token or device work.

1. Sign out of Teams.
2. Close the app fully from the taskbar.
3. Clear the correct cache path.
4. Restart Windows.
5. Open Teams and check for updates.
6. Try sign-in again with the expected work or school account.

Device and Admin Checks

Run dsregcmd /status

For this error, device sign-in state matters. Run the command below in a user context, not as a disconnected admin session. Microsoft’s PRT troubleshooting guidance says to inspect the SSO State section, confirm whether AzureAdPrt is YES, and check whether AzureAdPrtUpdateTime is older than four hours. If it is, the device is not refreshing the token as expected. [✅Source-9]

dsregcmd /status

• AzureAdPrt : YES means the device currently has a Microsoft Entra PRT.
• AzureAdPrt : NO means Teams may only be the visible symptom; the sign-in base is already unhealthy.
• Attempt Status helps identify the last acquisition or refresh failure.
• Correlation ID helps match the client event to tenant-side sign-in logs.

Microsoft’s device registration documentation also shows where these fields appear in the SSO State output and how failed PRT diagnostics are exposed after a bad refresh or acquisition attempt [✅Source-10].

Run Microsoft Sign-In Diagnostics

If you have admin access, use the Teams Sign-in diagnostic in the Microsoft 365 admin center first. Microsoft also provides the Teams Sign in test through the Remote Connectivity Analyzer. This is faster than guessing through manual steps when tenant configuration is involved.

Check Identity and Teams Endpoints

Authentication traffic must still reach Microsoft 365 identity services and Teams endpoints cleanly. Microsoft publishes required identity domains such as login.microsoftonline.com and enterpriseregistration.windows.net, and Teams service domains such as teams.microsoft.com and *.teams.microsoft.com. For desktop sign-in and web service access, TCP 443 is the first thing to verify. [✅Source-11]

Collect Client Logs

When basic fixes fail, collect logs before changing too many things. Microsoft now lets Teams admins request client logs remotely from the Teams admin center, view status centrally, and keep collected logs for 30 days. That is useful when the issue appears only on selected devices or only after idle time. [✅Source-12]

When the Broker Layer Is the Problem

Microsoft documents a repair step for cases where authentication fails because of missing or damaged WAM package information. For work or school accounts, the repair targets the Microsoft Entra WAM plugin. This is not the first fix to try, but it is a real fix path when the broker layer is unhealthy. [✅Source-13]

if (-not (Get-AppxPackage Microsoft.AAD.BrokerPlugin)) { Add-AppxPackage -Register "$env:windir\SystemApps\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\Appxmanifest.xml" -DisableDevelopmentMode -ForceApplicationShutdown } Get-AppxPackage Microsoft.AAD.BrokerPlugin

Run that only in the right scope, on the affected Windows device, and preferably after log collection. Randomly applying it across healthy devices makes troubleshooting harder.

Patterns That Often Trigger This Code

• PRT refresh stopped after the device sat idle, lost connectivity, or kept a broken broker state.
• Old account data remained in Teams cache or Windows credentials after a password change, tenant switch, or device reassignment.
• Wrong account context was selected locally, even though the user entered the right address later.
• Clock drift broke secure token exchange.
• Proxy, VPN, or filtered inspection interrupted Microsoft identity traffic over 443.
• Tenant-side policy required interaction, device compliance, or another control that the silent token path could not complete.
• Broker package damage affected more than Teams and showed up across Microsoft 365 apps.

A Clean Troubleshooting Order

1. Sign out of Teams and close it fully.
2. Clear the correct cache for Classic or New Teams.
3. Delete stale Windows credentials tied to the affected identity.
4. Sync date and time and confirm the time zone.
5. Update, repair, or reset Teams.
6. Run dsregcmd /status and inspect AzureAdPrt, AzureAdPrtUpdateTime, and Attempt Status.
7. Run Microsoft diagnostics for Teams sign-in.
8. Check 443 access to Microsoft identity and Teams endpoints.
9. Collect logs if the issue remains device-specific or intermittent.
10. Use WAM plugin repair only when evidence points to broker-level damage.

FAQ

Is 0xCAA90056 a Teams-only error?

No. Teams may be the visible app, but the error often points to a wider Windows and Microsoft Entra sign-in problem involving PRT, WAM, or cached credential state.

What does it mean if AzureAdPrt is NO?

It means the device is not holding a usable Microsoft Entra Primary Refresh Token for that user session. In that state, Teams desktop sign-in can fail even if the account itself is valid.

Should I clear the cache before reinstalling Teams?

Yes. Cache reset, sign-out, and credential cleanup are faster and often more effective than a full reinstall because the error often lives in local token or broker state, not only in app files.

When should an admin collect logs?

Collect logs when the error returns after basic cleanup, appears only on selected devices, or shows up after idle periods, password changes, or account switching. Logs help separate app damage from token-path damage.