This incident has been resolved.

Microsoft has implemented a fix that is mitigating login issues across the domain. We will continue to monitor the situation with them. Read more here: https://www.usatoday.com/story/tech/2020/09/28/microsoft-365-hit-major-outage-outlook-word-excel-and-teams/3568910001/

Our identity services provider has identified a problem with login across multiple systems. They are in the process of reverting the changes that caused the outage. We will post more information as it becomes available.