Azure MFA broke across the globe root cause still unknown.

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.