Hi omer ulker, I want to help you with this question.
If you have not backed up your old MFA entries in the Authenticator app, it is not possible to use the already activated MFA again when reinstalling the Authenticator app for security reasons. An MFA registration must be performed again. Since I assume that you have only one account, you cannot trigger the registration again from the portal.
What options are available to you if you log in again and click on "Forgot Password" instead of the password? Should you find alternative options to reset?
If there are no options, you would need to contact the Azure Data Protection team for further assistance - (866-807-5850) and have an issue created to reset the MFA.
In the future, I recommend creating an emergency account that is protected with a highly secure password and bypasses MFA. See also: https://learn.microsoft.com/en-us/azure/active-directory/roles/security-emergency-access
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