Users who require this add-in are advised to install Click-to-Run version of Office, as outlined in Office on Windows 10 in S mode article. If you are using an Office Outlook installation from the Microsoft Store, the Teams Meeting add-in isn't supported.If users do not see the Teams Meeting add-in, instruct them to close Outlook and Teams, then restart the Teams client first, then sign in to Teams, and then restart the Outlook client, in that specific order.User permissions to execute the Regsvr32.exe file is a minimum requirement for the Teams Meeting add-in to be installed on the computer.See Upgrade from Skype for Business to Teams for details. Under some circumstances, the Teams add-in is not available in Outlook.