Making it easier to apply and manage security settings for your users in Microsoft 365

Very sorry to hear about the difficulties.  All tenants created after October 2019 will have security defaults turned on when the tenant is created.  For the latest campaign to enable Security Defaults - before it's enabled, there should have been at least one email to the tenant admin in advance of the rollout along with one or more message center post notifications.  The Admin portal itself should show notifications to administrators about the change and a prompt to register for MFA.  If none of these indicators were seen, we'd certainly like to understand why.