These instructions will work for Outlook 2016 and 2019 and the current Office 365 version on Windows and macOS.
The below items require that you’re a member of the same organization or team.
For example, green means available, while red means currently in a meeting.
Fortunately, checking on it is straightforward.
First, click theFiletab on the Ribbon toolbar to go to the Backstage area.
Next, selectOptionstowards the bottom of the menu on the left.
Now selectAdd-insfrom the left side of the dialog.
You’ll see the screen shown below.
check that theMicrosoft Teams Meeting Add-inis not listed in theDisabled tool Add-inssection of the list.
If it is, selectDisabled Add-insfrom theManagedropdown and clickGo.
FindMicrosoft Teams Meeting Add-inin the list that appears, select it, clickEnable, then clickClose.
Once reactivated, you should get all the great Teams features the next time you re-start Outlook.