Because the authentication methods policy for Azure Active Directory provides the ability to manage methods for MFA and self-service password reset (SSPR) centrally, Microsoft retire the ability to manage authentication methods in the legacy MFA and SSPR policies on 30 September 2024. Please migrate to the authentication methods policy 

You can migrate Microsoft Entra ID legacy policy settings that separately control multifactor authentication and self-service password reset (SSPR) to unified management with the Authentication methods policy.

You migrate policy settings on your own schedule, and the process is fully reversible. You can continue to use tenant-wide MFA and SSPR policies while you configure authentication methods more precisely for users and groups in the Authentication methods policy. You complete the migration whenever you're ready to manage all authentication methods together in the Authentication methods policy.