"New Outlook" slider not longer available

Nice job on the New Outlook. Yesterday I updated it and was delighted to see the new look. 

For an unrelated issue, I had to Force Quit the client (password change issue). When it restarted, I no longer had access to the feature. All I get is the "Old Outlook". 

Is there a command line flag/setting that can be used to reactivate it?

I'm running this version on Catalina.