Microsoft is reporting this issue is now resolved.
Microsoft has identified the underlying cause of the problem and is taking steps to mitigate the impact. They will provide an updated ETA on the resolution as soon as one is available.
Microsoft is reporting that many users may be unable to access multiple Microsoft 365 services. Initial reports indicate the primary impact is to Microsoft Teams; however other services including Exchange Online are also impacted.
Microsoft is currently investigating the issue.
You may see the most recent updates at https://status.office.com/