@vishweshwar kanchangire Thank you for reaching out to us, would like to understand what happens when you click next, does it prompt you to register authenticator app.
If it is in authentication loop, usually you get into this state because of security defaults enabled on the tenant - https://learn.microsoft.com/en-us/entra/fundamentals/security-defaults
If your tenant was created on or after October 22, 2019, security defaults might be enabled in your tenant. To protect all of our users, security defaults are being rolled out to all new tenants at creation.
After this setting is enabled, all users in the organization will need to register for multifactor authentication.
If you dont have any other Global admin account who has access to the portal, in that case you need to contact our support team and create a case, work with Data protection team and Identity team to resolve this issue.
Let me know if you have any further questions, feel free to post back.