Team metting add in on outlook

Issue: Teams Meeting Add-in Fails Due to Missing Configuration File

We have recently experienced this issue across multiple PCs in the environment.

Problem

The Teams Meeting Add-in for Outlook fails to load correctly because a required configuration file is missing.

Root Cause

The file below is absent:

%LocalAppData%\Publishers\8wekyb3d8bbwe\TeamsSharedConfig\app_switcher_settings.json

When this file is missing, the add-in cannot verify that the New Teams client is set as the active application. As a result, the add-in shuts down during initialization.

Symptoms

From the add-in log located at:

%temp%\Microsoft\Teams\meeting-addin\

You may observe warnings similar to:

Warn: app_switcher_settings.json file does not exist or does not have value for defaultTeamsApp field.
Warn: Active Teams App set to Teams1

Note: The log incorrectly references the field name defaultTeamsApp. The correct field required in the JSON file is defaultApp.

Resolution / Workaround

Obtain a valid copy of the file app_switcher_settings.json from a working (healthy) machine.

Place it in the following directory:

%LocalAppData%\Publishers\8wekyb3d8bbwe\TeamsSharedConfig\

Ensure the file contains valid content, for example:

JSON

{"defaultApp":1,"cohort":"","webAccountId_AAD":"","cohortStage":"","userId_AAD":"","previousT1MachineId":"","previousT1SessionId":""}

Show more lines

Restart the applications in the correct order:

Close both Teams and Outlook

  Launch **Teams** first
  
     Then launch **Outlook**
     

Dear @Joseph Todorov,

Based on what you’ve described, this issue is commonly related to the Teams add‑in being disabled, not loading properly, or not installed correctly with the Teams desktop client.

In this case, could you please try the steps below:

1. Confirm your Outlook type

• If you are using the New Outlook, the Teams add‑in does not appear as a separate add‑in. Instead, you should see a “Teams meeting” toggle when creating a calendar event.
• If you are using Classic Outlook, please continue with the steps below.

2. Check if the Teams add‑in is enabled

• Open Outlook Classic
• Go to File > Options > Add-ins
• At the bottom, select COM Add-ins > Go
• Ensure Microsoft Teams Meeting Add-in for Microsoft Office is checked

3. Restart applications in the correct order

• Fully close Outlook
• Open and sign in to Microsoft Teams first
• Then launch Outlook again

4. Ensure Teams desktop app is installed

The add‑in requires the Teams desktop client (not just web version)

5. Reinstall Teams

• Uninstall Microsoft Teams
• Install the latest version
• Restart your device
• Open Teams first, then Outlook

For reference: Teams Meeting add-in is missing in Outlook Desktop after updating to New Teams

If the issue still persists after trying the above, could you please let me know:

• Are you using New Outlook or Classic Outlook?
• May I ask if this issue is affecting only your account, or multiple users?
• Could you please let me know what troubleshooting steps you have already tried?
• May I kindly check if any error code appears when you access the add-ins? If possible, please provide a screenshot for further review.

Appreciate your patience and understanding and thank you for your time and cooperation. Please feel free to reply below if you have any update or further concern.  

I am looking forward to your response!

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