The Systems team was asked if there were MFA issues after the user couldn't get a push notification, SMS message or call. Verified that there was an issue and Azure Status has documented the outage.
Impact: All users enabled for MFA in Azure will have issues reaching Office 365 hosted services if a new authentication event is required.
Affected Applications: All MFA enabled Office 365/Azure Services
13:00 27Nov2018 - Microsoft has identified the cause of this outage to be DNS. We are, internally, seeing MFA functioning. However, Microsoft is not saying that the issue is resolved, so the Systems team is still watching the issue.
08:22 AM 28Nov2018 - Microsoft has closed the incident and all MFA services are operational.