I have a Microsoft Account (which has an Office 365 Home subscription) that I have used to sign-up to the free Microsoft Teams, I was able to create a team and invite members using the web site. But after downloading the desktop app, and trying to sign-in, I no longer can do it, either with the desktop app or the web site. So, I am locked-out of the team that I created!
After hours of troubleshooting, I have found this article:
"I have an Office 365 subscription. Why can’t I access Microsoft Teams?
If you have a personal Office 365 subscription, you won't be able to access Microsoft Teams...."