The meeting coordinates (the Teams join link and dial-in numbers) will be added to the meeting invite after the user clicks Send. The Teams Meeting button in Outlook for Mac will appear in the Outlook for Mac ribbon if Outlook is running production build 16.24.414.0 and later and is activated with a Microsoft 365 or Office 365 client subscription. 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.