Microsoft Teams not launching after Windows update

2Method 2: Enable the Teams Meeting add-in in Outlook

If Teams or its integrated meeting features stop launching alongside Outlook, the Microsoft Teams Meeting Add-in for Microsoft Office may have been disabled automatically by Office.

1. Open classic Outlook on your desktop.
2. Click File in the top-left menu bar, then select Options near the bottom of the left list.
3. In the Outlook Options dialog box, click the Add-ins tab on the left.
4. Look at the Active Application Add-ins list to see if Microsoft Teams Meeting Add-in for Microsoft Office is listed. If it appears under Disabled Application Add-ins, proceed to the next step.
5. At the bottom of the window, locate the Manage drop-down menu, select COM Add-ins, and click Go.
6. In the COM Add-ins box, locate Microsoft Teams Meeting Add-in for Microsoft Office and click the checkbox next to it so a checkmark appears.
7. Click OK to close the window, then close and restart Outlook.

This method re-enables integration between classic Outlook and Teams. After restarting Outlook, the add-in will load automatically.

3Method 3: Reregister the Teams Addin Loader file

Illustration: the About page under Settings > System

When a Windows update breaks the connection between Teams and Office components, re-registering the DLL file restores the background startup handler. Note: Running Command Prompt commands modifies system file registrations, so follow the steps carefully.

1. Right-click the Start button and select Task Manager (or press Ctrl + Shift + Esc). Ensure both Microsoft Teams and Outlook are completely closed.
2. Open File Explorer from your taskbar and navigate to %LocalAppData%\Microsoft\TeamsMeetingAddin.
3. Look for subfolders named with version numbers. Click the subfolder with the highest version or build number (for example, 1.0.23334.11).
4. Click the address bar at the top of File Explorer, highlight the full folder path, and copy it to your clipboard.
5. Click the Start button, type cmd, right-click Command Prompt in the search results, and select Run as administrator.
6. For 64-bit Office, type the following command, replacing <path copied> with your copied path, and press Enter: %SystemRoot%\System32\regsvr32.exe /n /i:user <path copied>\x64\Microsoft.Teams.AddinLoader.dll
7. For 32-bit Office, type the following command instead and press Enter: %SystemRoot%\SysWOW64\regsvr32.exe /n /i:user <path copied>\x86\Microsoft.Teams.AddinLoader.dll
8. Restart the Teams desktop client, sign out of your account, and sign back in.
9. Restart Outlook (ensuring Outlook is not running in Administrator mode).

Re-registering Microsoft.Teams.AddinLoader.dll repairs missing entry points and allows Teams to launch without administrative conflicts.

4Method 4: Correct the LoadBehavior registry key

If Windows updates or policy shifts change your startup settings, the registry key governing Teams startup may be set incorrectly. Warning: Modifying registry entries incorrectly can cause system instability. Follow these instructions exactly.

1. Press Windows key + R on your keyboard to open the Run dialog box.
2. Type regedit into the box and press Enter or click OK.
3. In the Registry Editor window, navigate to the following path using the left sidebar: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Outlook\Addins\TeamsAddin.FastConnect
4. Locate the LoadBehavior entry in the right-hand panel.
5. Double-click LoadBehavior. In the Value data field, check the number. If it is set to anything other than 3, change the value to 3 and click OK.
6. Close the Registry Editor and restart your computer.

Setting LoadBehavior to 3 forces Outlook and Windows to load the Teams add-in automatically upon startup.

5Method 5: Reinstall the Teams add-in using Microsoft's PowerShell script

If you recently upgraded from classic Teams to the new Teams app, old add-in remnants can stop Teams from launching. Uninstalling the old add-in via PowerShell resolves conflicting installations.

1. Exit Teams and close Outlook.
2. Click Start > Settings > Apps > Installed apps.
3. Type Teams Meeting Add-in in the search box.
4. Check the version number displayed under Microsoft Teams Meeting Add-in for Microsoft Office.
5. If no result appears or the version starts with 1.23:
   • Download the UninstallOldTMA.ps1 PowerShell script from Microsoft.
   • Click Start, type powershell, right-click Windows PowerShell in the search results, and select Run as administrator.
   • Run the UninstallOldTMA.ps1 script in the PowerShell window.
6. If the version number does not start with 1.23:
   • Download the UninstallTMA.ps1 PowerShell script from Microsoft.
   • Click Start, type powershell, and select Windows PowerShell.
   • Run the UninstallTMA.ps1 script in the PowerShell window.
7. Launch the new Teams app and wait for the Teams Meeting Add-in to reappear under Installed apps.
8. Restart Outlook.

This script cleanly strips obsolete add-in builds so the new Teams desktop client can rebuild its local files correctly.

If nothing worked

If Microsoft Teams still refuses to launch, your installation might be impacted by a broader Microsoft account authentication issue, such as the sign-in bug originally identified under update KB5079473 (OS Build 26100.8037) which was resolved in KB5085516.

First, run the automated system troubleshooter by opening Settings > System > Troubleshoot > Other troubleshooters and running the Windows Update troubleshooter.

If the issue started immediately after a major monthly quality update, you can roll back the update temporarily. Open Settings > Windows Update > Update history > Uninstall updates, locate the most recently installed update, and click Uninstall. After rebooting, launch Teams to verify if functionality is restored while you wait for the next cumulative patch.