Many enterprises users across the globe were unable to sign into Microsoft Azure and Office 365 on Monday, as the result on ongoing multi-factor authentication (MFA) issues. The problem, which arose in the early hours of Monday morning and remains unresolved.
As per the last update Engineers have explored mitigating a back-end service via deploying a code hotfix, and this is currently being validated in a staging environment to verify before potential roll-out to production. Engineers are also continuing to explore additional workstreams to expedite mitigation.
More details and current status can be found here.