This is a requirement because COM add-ins to Outlook write to the Windows registry, and only administrators can modify the registry. One requirement for successfully installing the add-in on a Windows computer is that the user must have administrator permissions on the computer. Install the Teams app as an administrator of the Windows computer. Here are some steps to help you troubleshoot this problem. There are several reasons why the add-in may not display that have simple remedies. We’ve heard reports that the Microsoft Teams Meeting Add-in for Outlook on Windows does not show up for some users who have installed the desktop app.