@Claudia Salvador Jornet, Thanks for posting in Q&A. Currently MFA is enforced.
From your description, it seems the account has configured authentication by Microsoft Authenticator before on one Phone. So the two verify code in Microsoft authenticator on the phone you add your account is asked when you login your account. Please confirm if you have configured before.
Based as I know, the following page can set sign in method. You can click to see if it can access. If yes, you can remove the previous authenticator method and re-add it to configure authenticator on your own phone device.
https://mysignins.microsoft.com/security-info
Hope the above information can help.
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