Teams fails to complete installation correctly

I'm trying to install Teams on my Apple MAC.  I've downloaded the software and just as the installation completes, Teams starts up, but shows the error message below.

I have a licence for a Small Business O365 (persistent licence rather than subscription).  Teams isn't included with the licence, but I don't know if this is the issue.  Either way, I'm stuck here as I can't get passed this window.  If I click on the "sign out" link, it just fires up the same window with the same error.

Is anyone able to help, please?

- Dave.