Thank you for posting this in Microsoft Q&A.
1.Can you confirm which MFA options are available in legacy authentication methods and whether they are configured in the modern authentication methods policy?
2.Can you please check the modern authentication policy and confirm if all users are included in the MFA method or not? If possible, could you share a screenshot of the modern authentication policy?
You can be able to see Migration status over modern authentication policies page.
Thanks,
Navya