Hi Xiuyun Wang
Based on your description, it sounds like the account has been locked due to a security or verification policy, and since there’s currently no global admin assigned, you’ll need to regain access through an alternate verification method.
If your organization does not yet have an admin, please visit the Microsoft 365 admin takeover page and follow the steps under “Become the admin for your organization”. This process allows you to verify your domain ownership and establish yourself (or another authorized user) as the global admin. Once that’s completed, you’ll be able to unlock user accounts and manage administrative settings directly.
If you continue to experience issues during the admin claim process, please let me know which step you’re stuck on, and I’ll be happy to guide you further.
I hope this helps resolve your login problem! If you find this answer useful, please don’t forget to hit “Accept Answer” so others can benefit as well 😊