If New Teams Meeting option is unavailable on Outlook, follow the steps below.

Step 1. Open Outlook > File

Step 2. Click Options on the bottom left hand corner

Step 3. Click Add-ins

Step 4. Ensure the Manage tab is on COM Add-ins and click the box that says Go...

Step 5. Make sure the "Microsoft Teams Meeting Add-in for Microsoft Office" (highlighted in image below) box is toggled and click OK. Be advised, you may need to close the Outlook app and reboot your computer if it doesnt appear the first time.