Microsoft Teams is now down for some users around the world. Microsoft has acknowledged the outage. Microsoft has now informed users that it is investigating the issue where some users are unable to access Microsoft Teams. Microsoft will provide an update with further information soon.
Microsoft has identified the root cause of the issue. Microsoft has found that an authentication certificate has expired causing users who have logged out and those who that are still logged in to have issue using the service. Microsoft is preparing a fix to apply a new authentication certificate to resolve this issue as quickly as possible.