Teams Meeting Add-in Not Appearing in Outlook

For anyone still having the same issue, please try following this:

(This is from user u/kcheyne in reddit)

I ran into this yesterday and figured it out.

The file app_switcher_settings.json is missing from: %LocalAppData%\Publishers\8wekyb3d8bbwe\TeamsSharedConfig
Without it the meeting addin fails to confirm New Teams is the active client and shuts itself down on every load.

Diagnosis: Check the addin log at: %temp%\Microsoft\Teams\meeting-addin\

• Failure looks like:
• 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 error messages in this log field state a wrong field name "defaultTeamsApp". The correct fieldname needed in the json is "defaultApp"

Fix: Copy this file from a known-good machine and paste it in this path: * %LocalAppData%\Publishers\8wekyb3d8bbwe\TeamsSharedConfig\app_switcher_settings.json

Contents of the file that worked for me were this: {"defaultApp":1,"cohort":"","webAccountId_AAD":"","cohortStage":"","userId_AAD":"","previousT1MachineId":"","previousT1SessionId":""}

Then close both Outlook and Teams, launch Teams first, then Outlook.