Outlook for Windows is a pure web app, so you can't use COM addins, see here https://learn.microsoft.com/en-us/microsoft-365-apps/outlook/get-started/state-of-com-add-ins

The new Outlook for Windows doesn't support COM add-ins, but it does support Office web add-ins. To learn more about Office Add-ins, see Office Add-ins platform overview.

For guidance to migrate COM add-ins to web add-ins, see Migrate from COM to web add-ins.